'3 




Sass 

Book 



COPYRIGHT DEFOSIT 



HANDBOOK 

FOR 

HEATING AND VENTILATING 
ENGINEERS 



BY 
JAMES D. HOFFMAN, M. E. 

PROFESSOR OF PRACTICAL, MECHANICS AND DIRECTOR OF THE 

PRACTICAL MECHANICS LABORATORIES, PURDUE UNIVERSITY 

MEMBER AND PAST PRESIDENT A. S. H. & V. E. 

MEMBER A. S. M. E. 



ASSISTED BY 



BENEDICT F. RABER, B. S., M. E. 

PROFESSOR OF MECHANICAL ENGINEERING 

UNIVERSITY OF CALIFORNIA 

MEMBER A. S. M. E. 



FOURTH EDITION 

REWRITTEN AND RESET 



McGRAW-HILL BOOK COMPANY 

239 WEST 39TH STREET, NEW YORK 

6 BOUVERIE STREET, LONDON, E. C. 
1920 



(4 



^ 






Copyright, 1910, 1913, 1920 

BY 

JAMES D. Hoffman 



First Edition, 1910 
Second Edition, 1913 
Third Edition, 1917 
Fourtli Edition, 1920 



SEP - 
©C!.A5973a5 



PREFACE TO FOURTH EDITION. 

Changes in the art of heating- and ventilating buildings 
have been so pronounced in the last few j^ears that it has 
been considered advisable to entirely reconstruct the Hand- 
book rather than to make additions to the old text. The 
book, therefore, has been rewritten and reset in every part. 
There have been added approximately 87 pages consisting 
of revisions, extended discussions of original text and new 
subject matter not before considered. Of this increase, Chap- 
ter I has 17 pages, including discussions on heat applications, 
combustion of fuels and analysis of flue gases; Chapters II, 
III, IV and V on air measurements, heat losses and furnace 
heating have 19 pages devoted largely to extensions; Chap- 
ters VI, VII, VIII and IX on hot water and steam heating 
have 28 pages, increasing the original text of this part by 
approximately 43 per cent. This includes descriptions of 
modified gravity systems, both steam and water, valves, fit- 
tings and piping connections; Chapters' X, XI and Xll on 
mechanical warm air systems have 10 pages of extensions, 
and Chapter XIII has 4 pages of extensions to the calcula- 
tions of hot water and steam mains. The remainder of the 
book is in substance as it was with the addition of Sugges- 
tions to School Districts, 4 pages. Chapter XVIII, Suggested Pip- 
ing Connections for Vacuum System Details, 3 pages, Appendix 3, 
and several new tables on pipe sizes for hot water and 
steam service. 

Especial attention has been given to the simplification 
of every important subject by applications to practical prob- 
lems. These applications in most cases have been completely 
analyzed and their results compared with other parallel 
cases. No effort has been spared to have the entire subject 
matter complete and up to date and to present it in a way 
that will be at once simple and effective. 

This little book is as a growing child. We wish it to be 
very active and useful to the general public. To do this it 
must be versatile and resourceful, carrying no excess ma- 
terial and trained down to service condition. We ask the 
assistance of our friends and their suggestions in its behalf. 

LaFayette, Ind. J. D. H. 



EXTRACT FROM PREFACE TO FIRST EDITION. 

In the development of Heating and Ventilating- work, it 
is highly desirable that those engaged in the design and the 
installation of the apparatus be provided with a Handbook 
convenient for pocket use. Such a treatise should cover the 
entire field of heating and ventilation in a simplified form 
and should contain such tables as are commonly used in 
every day practice. This book aims to fulfill such a need and 
is intended to supplement other more specialized works. Be- 
cause of the scope of the work, its various phases could not 
be discussed exhaustively, but it is believed that the funda- 
mental principles are stated and applied in such a way as 
to be easily understood. It is suggestive rather than diges- 
tive. The principles presented are the same as those that 
have been stated many times before, but the arrangement of 
the work, the applications and the designs are all original. 
Many equations and rules are necessarily given; but it will 
be seen that, in most cases, they are developments from a 
few general equations, all of which can be readily under- 
stood and remembered. Practical points in constructive de- 
sign have also been considered. However, since the prin- 
ciples of heating and ventilation are founded upon funda- 
mental thermodynamic laws, it seems best to accentuate the 
theoretical side of the work in the belief that if this is well 
understood, practical points of experience will easily follow. 

All the standard works upon the subject have been 
freely consulted and used. In most cases where extracts are 
made, acknowledgment is given in the text. Because of 
these references throughout the book, we do not here repeat 
the names of their authors. We wish, however, to express 
our sincere appreciation 6f their valuable assistance. 

LaFayette, Ind. J. D. H. 



EXTRACT FROM PREFACE TO SECOND EDITION. 

A few corrections were made on the first edition and all 
the material has been revised and brought up to date. The 
work on air conditioning has been amplified. The descrip- 
tions of hot water and steam heating have been improved 
by diagrams of the various piping systems. Two chapters 
have been added on refrigeration and many tables have been 
added in the Appendix. Many suggestions coming from men 
in practice have been included, thus enlarging upon the prac- 
tical side and the applications. 

Lincoln. Neb. J. D. H. 



CONTENTS 



CHAPTER I. (Heat and Combustion) 
Arts. Pages 

1- 8 Introductory. Measurement of Heat and 

Temperatures 9- 16 

9- 17 Discussion of Heat and Heat Applications 17- 34 

CHAPTER II. (Air) 
18- 23 Composition of Air. Amount required per 

Person 35- 43 

24- 27 Humidity 44- 51 

28- 29 Convection of Air. Measurement of Air 

Velocities 52- 56 

30- 34 Air used in Combustion. Chimneys. Cowls.. 57- 60 

CHAPTER III. (Heat Losses) 
35- 42 Heat Losses from Buildings 61- 73 

43 Temperatures to be considered 73 

44 Heat given off from Lights and Persons 74 

45 Performance to Guarantee Heating Capacity 74- 75 

CHAPTER IV. (Furnace Heating) 

46- 47 Essentials of the Furnace System 76- 77 

48- 61 Calculations in Furnace Design 77- 85 

62 Application to a Ten Room Residence 86- 91 

63 Determination of Best Outside Temperature 92- 94 

64 Humidifying Furnace Air 95- 99 

CHAPTER V. (Furnace Heating, Continued) 

65- 66 Selecting, Locating and Setting the Furnace 100-105 

67- 72 Air Ducts. Circulation of Air in Rooms 106-112 

73 Fan Furnace Heating 113-114 

74- 75 Hot Air Radiator Systems 115-117 

76 Improving Sluggish Circulation 117 

77 Suggestions for Operating Furnaces 118-119 

CHAPTER VI. (Hot Water and Steam Heating) 

78- 81 Comparison and Classification of Systems 120-125 

82 Diagrams of Piping Systems 125-130 

83- 85 Modified Gravity Systems 130-140 

86 Standard Piping Connections 141-143 



CHAPTER VII. (Hot Water and Steam Heating, Cont'd) 
Arts. Pages 

87- 88 Heaters, Boilers and Accessories 144-150 

89- 95 Classification and Efficiencies of Radiators. ...150-157 

96 Pipe and Fittings 157-163 

97- 99 Expansion Tanks, Fire Coils and Corrosion. ...163-165 

CHAPTER VIII. (Hot Water and Steam Heating, Cont'd) 
100-104 Calculations for Boiler Size and Radiator 

Surface 166-177 

105 Greenhouse Heating 177-180 

106-107 Determination of Pipe Sizes 180-184 

108-109 Pitch of Mains and Radiator Connections 184-185 

110 General Application to Hot Water Design 185-191 

111-112 Insulating Steam Pipes. Water Hammer.. ...'.. .191-193 

113 Feeding Return Water to Boiler 193-198 

114 Hot Water Heating for Tanks and Pools 198 

115 Suggestions for Operating Boilers 198-199 

CHAPTER IX. (Mechanical Vacuum Heating) 
116-117 General. Return line and Air line Systems 

Described .'200-204 

118 Vacuum Pumps and Regulation 205-208 

119 Vacuum Specialties 208-212 

CHAPTER X. (Mechanical Warm Air Heating) 
120-124 General Discussion. Blowers and Fans. 

Heating Surfaces 213-223 

125-128 Single and Double Duct Systems. Air 

Washing 223-233 

CHAPTER XI. (Mechanical Warm Air Heating, Cont'd) 
129-133 Heat Loss. Air Required. Air Tempera- 
tures 234-237 

134-135 Air Velocities. Area of Ducts 237-238 

136-140 Heating Surface in Coils. Arrangement of 

Coils 238-247 

141-143 Amount of Steam Used in the System 247-248 

CHAPTER XII. (Mechanical Warm Air Heating, Cont'd) 
144-148 Air Velocity and Pressure. Horse-Power 

in Moving Air 249-260 

149-154 Fan Sizes and Drives. Speeds. Size of 

Engine. Piping Connections 260-266 

155-156 General Application to Plenum System 267-274 



CHAPTER XIII. (District Heating) 
Arts. Pages 

157-161 General. Conduits. Expansion Joints. 

Anchors 275-289 

162-164 Typical Design. Heat in Exhaust Steam 289-295 

165-168 Hot Water Systems. General Discussion 296-298 

169-171 Pressure and Velocity of Water in Mains 298-303 

172-176 Radiation Heated by Exhaust Steam 304-306 

177-182 Reheating Calculations 306-312 

183-186 Circulating Pumps. Boiler Peed Pumps 313-318 

187-191 Radiation Supplied by Boilers and Econ- 
omizers 319-323 

192 Total Capacity of Boiler Plant 323-326 

193-195 Cost of Heating from Central Station. 

Regulating the Heat Supply ,. 326-332 

19G Steam System. General Discussion 332-333 

197-199 Pipe Sizes. Dripping the Mains 334-338 

200 General Application of Steam System to 

District 338-340 

CHAPTER XIV. (Temperature Control) 
201-204 General. Johnson, Powers and National 

Systems 341-349 

CHAPTER XV. (Electrical Heating) 
205-207 Discussion and Calculations 350-352 

CHAPTER XVI. (Refrigeration) 

208-209 Discussion of Systems 353-354 

210-211 Vacuum and Cold Air Systems 354-355 

212-213 Compression and Absorption Systems 355-358 

214 Condensers 359-361 

215 Evaporators 361-363 

216 Pipes, Valves and Fittings 363 

217-218 Absorption System 364-367 

219-220 Generators 368-369 

221-225 Condensers, Absorbers, Exchangers and 

Pumps 369-371 

226-227 Comparison of Systems 372 

228 Methods of Maintaining Low Temperatures.. 373-374 

229 Influence of Dew Point 375-376 

230-231 Pipe Line Refrigeration 376-377 



CHAPTER XVII. (Refrigeration, Continued) 
Arts. Pages 

232-234 Calculations 378-382 

235 General Application .- 383-384 

236-238 Method of Rating Capacity 384-385 

239 Cost of Refrigeration 385-387 

CHAPTER XVIII. (Specifications) 

Suggestions on Planning Specifications 388-394 

Suggestions to School Districts 395-398 

APPENDIX I. 
Tables 1-57 399-452 

APPENDIX II. 
Tables 58-75 453-463 

APPENDIX III. 

Test of House Heating Boilers and Data 
Required for Estimating Hot Water and 
Steam Boilers 465-467 

Details of Vacuum Piping Systems 468-470 



CHAPTER 1. 



HEAT — ITS NATURE, GENERATION, USE, MEASUREMENT 
AND TRANS3IISSION. 



1. Introductory: — In all localities where the atmosphere 
drops in temperature much below 60° Fahrenheit, there is 
created a demand for the artificial heating of building's. As 
the buildings have grown in size and complexity of con- 
struction, so also this demand has grown in extent and pre- 
ciseness, with the general result that out of the open fire 
place and iron stove there has developed a science growing 
richer each day from inventive genius and manufacturing 
technique — the science of the heating and ventilating of 
buildings. The purpose of this handbook shall be to out- 
line the fundamental principles and practical applications of 
this science in its various branches. 

To the average heating engineer it may be that the 
exact nature of heat itself is of much less moment than its 
generation and transmission, but these facts should be im- 
pressed, — that heat is one form of molecular energy, that it 
cannot be created except by conversion from some other 
form, and that it is infallibly obedient to certain physical 
laws and principles which should be understood and used 
by every engineer. 

In generating heat for heating purposes the almost uni- 
versal method is combustion. The union of the combustible 
content of such substances as coal, wood or peat with the 
oxygen of the air is always attended by a liberation of heat 
derived from the chemical action of the combination; and 
this heat is carried by some common carrier, such as air, 
water or steam, to the building or room to be heated where 
it is given off by the natural cooling process. In some in- 
stances this heat is converted into electrical energy which 
is carried by wire to the place of use and given off as heat 
through a set of resistance coils. This method is not much 
favored as yet because of its inefficiency and the resulting 
expense, an objection which does not hold in the case of 
water power installations where the combustion of fuel is 
entirely eliminated. 



10 HEATING AND VENTILATION 

2. Heat— Temperature : — The meaning of the word heat 
should not be confused with that of the word temperature. 
Although closely related they are far from being inter- 
changeable. In a given mass of any substance, except 
when passing through a change of state, the universal law 
is that the addition of heat raises the temperature and the 
subtraction of heat lowers the temperature of the sub- 
stance. Heat is the cause and temperature is one of the 
effects. In the measurement of heat the most commonly 
accepted unit in practical engineering work is the British 
thermal unit, abbreviated B. t. u. This may be defined as 
that amount of heat which will raise the temperature of one pound 
of pure water one degree Fahrenheit (See definition for specific 
heat, Art. 8). This unit value, the B. t. u., measures the 
quantity of heat, while the temperature measures the inten- 
sity or degree of heat. In equal masses of the same sub- 
stance the two are proportional. The Fahrenheit scale is the 
more commonly used temperature scale, especially in steam 
engineering. The unit of this scale is derived by dividing 
the distance on the thermometer between the freezing point 
and the boiling point of water into 180 spaces called de- 
grees, the freezing point being marked 32° and the boiling 
point 212°. All temperatures in this took, unless otherioise stated, 
vnll be taken according to the Fahrenheit scale and all quantities 
of heat expressed in British thermal units. 

A second unit of quantity of heat considerably used in 
scientific research is the calorie, abbreviated cal., and defined 
as that amount of heat which \vill raise one kilogram of 
pure water from 17° to 18° centigrade. The centigrade scale 
is a second temperature scale, the unit of which is derived 
by dividing the distance on the. thermometer between the 
freezing point and the boiling point of water into 100 de- 
grees, the freezing point being marked 0° and the boiling 
point 100°. 

It is often found desirable to change the expression 
for temperature or for quantity of heat from one system 
of terms to that of the other. For this purpose the follow- 
ing equations will be found useful: 

9 5 

F = — C + 32 and C = (F — 32) — (1) 

5 9 

where F = Fahrenheit degrees and C = centigrade degrees. 
From these equations it may be seen that the two scales 



MEASUREMENT OF TEMPERATURE 11 

coincide at but one point, — 40°. For conversion of the 
quantity units the following may be used: 

1 British thermal unit = 0.252 calorie. 
1 calorie = 3.968 British thermal units. 
These are for the absolute conversion of a certain quantity 
of heat from one system to the other. If, however, the effect 
of this heat is considered upon a given weight of substance 
and the weight also is expressed in the respective systems, 
the following values hold: 

1 calorie per kilogram = 1.8 British thermal units 
per pound. 

1 British thermal unit per pound = 0.555 calorie 
per kilogram. 
For conversion tables see Marks' Mechanical Engineers' 
Handbook or Kent's Mechanical Engineers' Pocket-Book. 

3. Instruments Used in Pleasuring' Temperature: — In- 
struments intended to indicate degree or intensity of heat, 
i. e., the teniperature of substances, are designed upon many 
different principles. Of these the following represent the 
important general classifications: 

Expansion of a Liquid with Inckease in Temperature. — The 
ordinary mfercury, alcohol or ether-in-glass thermometers be- 
long to this great class. Mercury thermometers should not 
be used to register temperatures near the top of the scale 
for fear of rupturing the glass. To overcome this difficulty 
some thermometers are made with a mercury-well at the 
upper end of the mercury column. The objection to be 
offered to this form is the difficulty of completely emptying 
the upper well after it has been partially or wholly filled 
with mercury. The ordinary mercury-in-glass thermometer, 
either with or without, the upper mercury- well, should not 
be used on temperatures above 600° F. because of the fact 
that mercury boils at 680° F. Mercury-in-glass or mercury- 
in-quartz thermometers have been used up to 1300° F. by 
compressing into the space above the mercury some neutral 
gas, as nitrogen or carbon dioxide. This type, however, is 
open to the objection of high breakage costs. Due to the 
fact that inercury freezes at — 38° F. it cannot be used for low 
temperature thermometers. These are usually made with 
alcohol as the liquid, since alcohol freezes at — 170° F. 

Expansion of a Solid with Increase in Temperature. — In- 
struments built upon this principle are commonly called ex- 
pansion pyrometers. Fig. 1, a, shows such a pyrometer. Inside 



12 



HEATING AND VENTILATION 



the stem of the instrument is a metallic expansion element, 
the movement of the free end of which operates the hand on 
the dial. Such an instrument may be used up to the lowest 
temperature of the softening point of the metals in the stem. 
Ordinarily, errors of 2 to 5 per cent, may be expected in the 
temperature reading-. 






Fig. 1. 

Fusion of Cones of Refractory Materials. — This principle 
is exceedingly simple in application as shown in Fig. 1, b. 
Several of a series of cones, varying in mineral compositions 
and hence in melting points, are exposed to the temperature 



MEASUREMENT OF TEMPERATURE 13 

to be measured and this temperature is indicated by that 
cone of the series which just melts or softens sufficiently to 
lose its shape. With the cones is furnished a table of tem- 
peratures for comparison. From the illustration, the tem- 
perature indicated is evidently that corresponding- to cone 
number 08, which from the Seger cone table is 1814° F. 
Seger cones for such measurements may be obtained to indi- 
cate temperatures from 1094° F. to 2800° F. by increments 
varying- from 25 to 55 degrees. 

Transfer of a High Temperature Body and its Heat to a 
Known Quantity of Water. — This is the principle embodied in 
all pyrometers of the caJorimetric type, one of w^hich is shown 
in Fig-. 1, c. A thoroughly insulated vessel contains a known 
quantity of water, a thermometer and a stirring device. A 
ball of platinum, copper or iron of known weight and 
specific heat is exposed to the temperature to be measured, 
by means of the handle shown in the figure or by a small 
crucible. When the ball has reached its upper temperature, 
it is quickly transferred to the water of the insulated vessel 
and the rise of temperature of the water is noted from the 
thermometer. Upon the suppositions that all the heat in 
the ball is transferred to the water and that the ball and 
the water finally reach the same temperature, the assump- 
tion may be made that the heat gained by the w^ater equals 
that lost by the ball, hence the product of the weight, tem- 
perature rise and specific heat of the water, divided by the 
product of the weight and specific heat of the ball gives the 
drop in temperature through which the ball has passed. 
From this the upper temperature reached by the ball may 
be obtained by adding to the temperature drop, the final 
temperature of the water and the ball. Let s = specific heat 
of the ball, T = upper temperature of ball, m = weight of 
the ball, * and f respectively = beginning and ending tem- 
peratures of the water, and w = weight of the water. 
Remembering- that the specific heat of water is 1, we have 
IV (f — t) = sm (T — f) whence (2) 

w if — *) 

T = • + r 

sm 

The objections to this method of temperature measurement 

are its slowness due to the necessary computations and 

manipulations, and the fact that considerable error may be 

introduced during- the transference of the ball from the 

heated space to the calorimeter. When this method is used 



14 HEATING AND VENTILATION 

for very high temperatures the ball is made of porcelain or 
fire clay. 

Change of Resistance of an Electric Conductor, or Change 
OF Voltage of an Electric Thermo-couple. — Instruments built 
upon either of these two electrical principles are extremely 
delicate but give very accurate results, it being possible to 
determine temperatures up to 2000° F. with a variation of 
but one or two degrees. For practical work electric pyrom- 
eters are more commonly of the tlier mo- couple type (See Fig. 
1, d). To the right is shown a porcelain tube enclosing a 
thermo-couple of two dissimilar metals. If this tube is 
subjected to the temperature to be measured, the potential 
generated by the couple upon heating is proportional to the 
temperature. Hence, if connected to a voltmeter as shown 
at the left, the voltage generated may be indicated, or as 
is usual, the temperature may be read directly since the 
scale of the voltmeter may be graduated in degrees instead 
of in volts. This type of pyrometer is extensively used. 
From each of a large number of testing points, thermo- 
couple wires may be brought to a central point, where by 
means of a sw^itch the temperature at any couple may be 
instantly observed by throwing its current into a common 
voltmeter or temperature indicator. 

Other types of temperature measuring instruments are 
designed upon the principle of the optical pyrometer, and 
the gas and air therinometers, but these are not used to as 
large an extent in practice as are the five above mentioned. 

4. Absolute Temperature: — In experiments that have 
been carried on with pure gases with the use of air ther- 
mometers, it has been found that gases expand or contract 

1 1 

approximately — of their volumes at 32° F. ( of their 

492 460 
volumes at zero F.) per degree change in temperature, or 
1 

• of their volumes at zero C. From the same line of 

273 

reasoning, by cooling a gas to — 460° F. or — 273° C, it 
would cease to exist. This theoretical point is called the 
absolute zero of temperature. All gases change to liquids 
or solids before this point is reached, however, and hence 
do not obey the law of contraction of gases at very low 
temperatures. The fact that air at constant pressure 
changes its volume almost exactly in proportion to the abso- 
lute temperature, T, (460 + t, where t is temperature Fahr- 



MECHANICAL EQUIVALENT OF HEAT 15 

enheit) gives a starting point to be used as a basis for all 
air volume-temperature calculations. For instance, if a 
volume of 20000 cubic feet of air at 0° is heated to 70° 
with constant pressure, its volume after heating will be 
greater in the same proportion as its absolute temperature 

w 530 

is greater; that is, = ; x = 23000 cubic feet, or 

20000 460 

an increase of 15 per cent. 

5. Gage and Absolute Pressures: — Gage pressure is the 
total pressure per square inch in a container minus the 
pressure of one atmosphere. Thus 65 pounds gage pressure 
means that the container is carrying 65 pounds pressure per 
square inch of surface above the pressure of the atmosphere. 
Atmospheric pressure at sea level, 14.696 commonly written 
14.7, is used on all but the most exact calculations. This 
pressure becomes less as the elevation rises above sea level. 
As a general statement it may be said that atmospheric 
pressure reduces Yz pound for each 1,000 feet above sea level 
(See Table 8, Appendix). The total pressure exerted within 
the container is therefore 65 + 14.696 = 79.696 at sea level. 
This total pressure is known as the ahsolute pressure and 
when stated in pounds per square foot of area is called 
specific pressure. 

Q. Meohanieal Equivalent of Heat: — By experiment it 
has been determined that if the heat energy represented by 
one B. t. u. be changed into mechanical energy without loss, 
it would accomplish 778 foot pounds of work. Similarly, one 
calorie is equivalent to 428 kilogrammeters of work. 

7. Latent Heat, Total Heat, Etc.: — Not all the heat 
applied to a body produces change in temperature. Under 
certain conditions the heat applied produces internal or 
molecular changes and is called latent heat. Thus in a nor- 
mal atmosphere if heat is applied to ice at the freezing 
point, no rise of temperature is noted until all the ice is 
melted; and again, heat applied to water at the boiling 
point does not raise its temperature until all the water is 
changed to steam. The first is called latent heat of fusion, 
which for ice is 144 B. t. u. per pound; the latter is called 
latent heat of vaporization, which for water is 970.4 (Marks 
and Davis) B. t. u. per pound. For most calculations the 
approximate value 970 may be used. Consult books on ther- 
modynamics for further discussion of latent heat as com- 
posed of internal and external work equivalents. Sensible Jieat 



16 HEATING AND VENTILATION 

is that heat whose addition or subtraction can be detected 
by a thermometer. As applied to the standard steam tables, 
this is equal to the total heat above 32° minus the latent 
heat of vaporization. Heat of the liquid, as applied to the 
standard steam tables, is that quantity of heat added to a 
pound of water at 32° to bring- it to the temperature of the 
boiling point at any given pressure. At atmospheric pres- 
sure this is 180 B. t. u. Total heat is that quantity of heat 
represented by the sum of the latent heat of vaporization 
and the heat of the liquid. In the evaporation of water at 
atmospheric pressure this is 970.4 + (212 — 32) = 1150.4 
B. t. u. Total heat is different for all pressures at which 
evaporation takes place. Consult Art. 14 and Table 4, Ap- 
pendix, for latent heat, heat of the liquid and total heat at 
different pressures. 

Convenient approximate equations for latent heat and total 
heat are those quoted by Regnault. 

Latent Heat = 1092 — .695 (t — 32) (3) 

where t = temperature at which the steam is formed. 

Illustration. — The latent heat of steam at a temperature 
of 338° (pressure 100 lbs. gage) is 1092 — .695 (338 — 32) = 
879.3 B. t. u. 

Total heat = 1092 -\- .305 (t — 32) (4) 

Illustration. — The total heat above 32° of the same steam 
as in previous illustration is 1092 -j- .305 (338 — '32) = 1185.3. 

8. Specific Heat: — The specific heat of a substance is 
that quantity of heat added to or subtracted from a unit 
weight of the substance when its temperature is changed 
one degree. The mean specific heat is that quantity of heat 
added to or subtracted from a unit weight of the substance 
in changing through any given number of degrees, divided 
by the number of degrees change. For illustration, the 
specific heat of water that has been considered standard for 
many years is obtained at the temperature of its maximum 
density, 39.1° F. (4° C). This is used in much of the physi- 
cal and scientific calculations, but in most engineering w^ork 
the tendency is to take the mean specific heat between the 
temperatures of 32° F. and 212° F. (0° C. and 100° C), i. e., 
the heat required to raise one pound of pure water from 32° 
F. to 212° F. divided by 180. This is the same as the specific 
heat of water at 62° F. and agrees with the accepted value 
of the B. t. u. Table 26, Appendix, gives specific heats of 
substances. 



RADIATION 17 

9. Radiation: — Heat may be transmitted as a wave mo- 
tion in the ether of space. In this way the heat of the sun 
reaches the earth. Heat of this form, usually referred to as 
radiant heat, requires no matter for its conveyance; passes 
throug-h some materials, notably rock salt, without change 
or appreciable loss; and follows the laws for the radiation of 
light. It is assumed that the heat received by the atmos- 
phere is obtained through contact with the bodies giving- 
and receiving heat and that little is obtained directly from 
the radiant ray. 

TABLE 1. 
Radiation Constants, Values of C 

Material C 

Glass, smooth 0.154 

Brass, dull 0.0362 

Copper, slightly polished 0.0278 

Lampblack 0.154 

Wrought-iron, dull, oxidized 0.154 

"Wrought-iron, clean, bright 0.0562 

Cast iron, rough, highly oxidized 0.157 

Lime plaster, rough, white 0.151 

Slate 0.115 

Gold plate, shining but not polished 0.082 

Clay 0.065 

The capacity that any body has of absorbing the radiant 
ray is called its absorption capacity. Absolute black bodies 
theoretically absorb all the radiation received upon their 
surfaces and have an absorption capacity of 1. Bright or 
polished surfaces have a reduced absorption capacity. It is 
also understood that the radiation capacity is proportional to 
the absorption capacity. The amount of heat radiated by a 
substance is practically independent of the form of the sur- 
face and depends upon the difference of temperature be- 
tween the radiating and receiving" surfaces, and upon the 
color and character' of the surfaces. The Stefan-Boltzman 
radiation law states that for black bodies the radiating 
power is proportional to the fourth power of the absolute 
temperature of the body. For other than black bodies this 
law is also approximately true. Let R = area of radiating 
surface in square feet, i? = B. t. u. radiated per hour, T = 



18 HEATING AND VENTILATION 

absolute temperature of the substance, and C z= a, constant; 
then, n = CR (T -^ lOO)*. For a dead black body C = .1618. 
Other values of C from Hutte are shown in Table 1. 

Assuming- in general that radiating surfaces for heating 
systeins may be classified as black bodies, the amount of 
heat radiated from a surface R having an absolute tempera- 
ture T to surrounding surfaces having an absolute tempera- 
ture Ti is 

H = C R liT ^ 100)4 _ (y^ ^ 100)*] 

Applications of the theoretical formula of radiant heat to 
practical problems in general give very unsatisfactory re- 
sults. 

10. Conduction: — This method of heat transmission !s 
very evident to the senses. If a rod of metal is heated at 
one end, the heat is transferred or conducted along the rod 
by molecular action. Conduction being essentially the -way 
by which solids transfer heat, it is of special significance in 
the calculation of heat losses through the walls of a build- 
ing. The coefficient of conduction may be defined as that quan- 
tity of heat which passes through a unit thickness of 
substance in a unit of time across a unit of surface, the dif- 
ference of temperature between the two sides of the sub- 
stance being one unit of the thermometric scale employed. 
The amount of heat conducted through a material in a 
given time is directly proportional to the difference in tem- 
perature between the two parallel sides of the substance 
and inversely proportional to the thickness. As a formula 
H =z c/h (ti — • to) where c = coefficient of conductivity, 6 = 
thickness of material in inches, and fi and ^2 = respective 
temperatures. Since the complexity of building construc- 
tions renders it impossible to reduce all conduction losses 
to losses per unit thickness of the structure, the term rate 
of transmission may be used instead of conductivity and may 
be understood to include combinations of conductivities and 
thicknesses. This may be illustrated by the ordinary 
framed and studded wall where K is the rate for the com- 
bination (See Chapter III). 

11. Convection: — Gases and liquids convey heat most 
readily by this method, -which is fundamental w^ith warm air 
and hot water heating installations. If it is attempted to 
heat a body of water by applying heat to its upper surface, it 
will be found to warm up with extreme slowness. If, however, 



WORK AND POWER 



19 



the source of heat be applied below the body of water, it 
will be found to heat rapidly. What actually happens is 
this: water particles near the source of heat become lighter, 
volume for volume, than the colder particles near the top, 
and because of the change in density gravity causes an 
exchange of these particles, drawing the heavier to the bot- 
tom and allowing the heated and lighter particles to rise to 
the top thus forming circulation currents. This process is 
known as convection. It will not occur unless the medium 
expands upon being heated and unless the force of gravity 
is free to establish circulating currents. In the hot water 
heating system (Fig. 2), water rises by convection to the 
radiators, is there cooled and descends by the 
return circuit to the point of heat application 
completing the circuit. The warm air furnace 
installation works similarly, air, however, being 
the heat-carrying medium. 

13. "Work: — Work is the overcoming of a resist- 
ance along a line of motion. It is the product of 
force and distance and is independent of time. 
Assuming the pound to be the unit of force and 
the foot to be the unit of distance, the unit of 
work is the foot-pound. To lift one hundred 
pounds one foot or one pound one hundred feet 
would cause the expenditure of one hundred foot 
pounds of work. 

XS. PoTt^er: — Power and work are closely re- 
lated but are not identical. Power is the rate of 
doing work, and always comprehends the element 
of time. The unit of power, called horse-potoer. 




^ 



ry 



Fig. 2. 

has no reference to the power of the horse nor to the boiler 
horse-power, but is an arbitrary value equivalent to 
1 horse-power — 
746 Watts = .746 K. W. 
33000 ft. lbs. of work per min. 
4562.4 kilogrammeters of work per min. 
33000 -^ 778 = 42.416 B. t. u. per min. 
4562.4 -f- 428 = 10.66 cal. per min. 

If 100 cubic feet of water, weighing 62.5 pounds per cubic 
foot, are lifted 100 feet per minute without friction loss, the 
horse-power is (100 X 62.5 X 100) H- 33000 = 18.94. 

The term holler horse-po^oer is equivalent to 34.5 pounds 



20 HEATING AND VENTILATION 

of water per hour evaporated from water at 212° F. to 
steam at 212° F. This equals 970.4 X 34.5 r= 33479 B. t. u. 

14. Application of Heat to Solids and Liquids: — ^All 
matter in its most finely divided state is made up of minute 
particles called atoms which are drawn together by a force 
called attraction. This attraction is lessened by the applica- 
tion of heat, the particles tending- to separate (substance 
increasing in size) until such a temperature is reached (a 
certain amount of heat is absorbed) when the attraction is 
zero. From this point further application of heat will cause 
repulsion and the particles will fly apart. This explains the 
existence of the three states of matter; solid, liquid and 
gaseous. No two substances act exactly alike upon the 
addition or subtraction of heat, but practically all sub- 
stances under certain conditions may exist in any one of 
the three states. The exact points of separation between 
the solid, liquid and gas, differ very much in different sub- 
stances; but regardless of this fact, each substance no mat- 
ter what its state may be solidified by cooling or vaporized 
by heating. The amount of heat that may be carried by 
any substance in any given state is called its capacity for heat. 

When solids change in temperature they change in vol- 
ume in practically all cases, increasing with rise of tempera- 
ture and decreasing with fall of temperature. This fact 
many times causes considerable annoyance to any one manu- 
facturing or using materials of construction. Since all 
metals that enter into engineering construction are subject 
to sudden and sometimes very extreme changes of tempera- 
ture, it is frequently necessary to put in compensating de- 
vices to account for such temperature changes. The steel 
framework of a building for example is subjected to ex- 
tremes of summer and winter temperatures, causing change 
in the building size. This change is small, but during the 
cold weather when the building materials have a slight re- 
duction in size, the steam pipes are under high temperatures 
and have their maxirnum size. During the summer when 
no heat is necessary, reverse conditions exist. In high 
buildings this change is sufficient to demand compensators 
or expansion joints in the steam lines, otherwise there 
would be contact between the pipes and the building which 
might be sufficient to rupture some part. Like conditions 
exist in street mains (conduit lines), basement mains in 
buildings, horizontal connections between vertical risers, 



APPLICATION OF HEAT TO LIQUIDS 



21 



riser connections between floors, boiler pipe connections, 
boiler settings in brick Avork and in many other places 
around the heating- system of the average building. 

Sudden changes of temperature in any material are to 
be avoided when possible. This is especially true if the 
materials are fastened together with screws, bolts or rivets, 
such as boilers, heaters or piping systems. When heat is 
thus applied it is always more intense at one place than at 
another and the expansion or contraction is not uniform, 
causing unnecessary stresses and many times leaks and rup- 
tures. The force exerted hy heat in expanding any substance 
is the same as would be required to stretch the same sub- 
stance an equal amount by mechanical means or to compress 
the enlarged piece to its former size. 

When heat is applied to liquids, the phenomenon of ex- 
pansion is apparent as in solids. One notable exception is 
found in water between 32° and 39.1° F. as will be seen 
later. Since water is the liquid universally used in heating systems, 




unk T Per ^^lume of 
Per Lb. FkrLb. Pound I Pound at Water 



Units 
Per Fbund 



Units P^ 
Pound 



VoLUME^TEMPERflTURc- State Ch/v^e OF Water Uhdeh /\TMoePHERic Pressure. 



Fig. 3. 
it is of interest to study its characteristics under different conditions 
of heat. Start with a mass of one pound of ice at some tem- 
perature, say 25° F. (it must be remembered that after ice 
is formed at 32° F. it may be cooled to any temperature 
below 32° by the continued extraction of heat), and while 
heat is being added to the mass, note the changes taking 
place. In Fig. 3 EFGABK is the temperature curve, LMNOC is 
the volume curve, the ordinates MM', NN', OD and BC represent 



22 HEATING AND VENTILATION 

the periods of change of state, and the horizontal line at the 
base of the chart L'C represents heat units added. With LL' 
representing the volume of a pound of ice at any tempera- 
ture (in this case 25° F.) heat is added and the temperature 
curve E rises to F. The quantity of heat added is found by 
multiplying- the pounds of ice (in this case 1) by the specific 
heat, which for ice is .504, and by the rise in temperature. 
The addition of .504 B. t. u. for each degree rise between 
25° and 32° gives the ice (32 — 25) X .504 = 3.528 B. t. u. 
and brings it to the temperature of the melting point. "While 
the temperature has been gradually increasing the volume 
has also increased slightly. See MAI'. More heat is added 
and the ice begins to melt but the temperature does not 
rise as "would be expected. It remains constant from i^ to G^ 
until all the ice has changed to water, as shown by the line 
MN'. In this change there has been a reduction in the vol- 
ume of the mass as shown by the dropping of the line MN. 
Notice that the volume of the water is taken as 1 and the 
volume of the ice at 32° as 1.09. This explains why water 
allowed to freeze in a pipe often causes the bursting of the 
pipe. The quantity of heat absorbed during the change of 
state from ice to water without change of temperature is 
found by experiment to be 144 B. t. u. per pound and is 
called the latent heat of fusion. Conversely, in the reverse 
change the same amount of heat would be given off. So far 
we have added to the pound of ice 3.528 + 144 =: 147.528 
B. t. u. and have increased the temperature only 7 degrees. 
From this point ONN', where the entire mass is water with a 
volume approximately equal to 1, the addition of heat causes 
a uniform rise in temperature along OA; also a slight de- 
crease in volume along MN to the point of maximum density 
39.1°, where the volume NN' is 1, and from here a uniform 
increase in volume along NO until the temperature has risen 
from 39.1° to 212° and the volume has increased from 1 to 
1.034, with an addition of 212 — • 32 = 180 B. t. u. To arrive 
at the state line AOD required the addition of 3.528 + 144 + 
180 = 327.528 B. t. u., and a total of 187 degrees change. 
At AOD a second change of state is encountered. 970.4 
B. t. u. (latent heat of vaporization) are now added to the 
pound of w^ater without changing its temperature and the 
mass has a uniform change of state from water at 212° to. 
steam at 212°. When the temperature line reaches B the 
volume line of the water is at C, indicating that all the 



APPLICATION OF HEAT TO LIQUIDS 



23 



water has become steam at atmospheric pressure and now 
occupies a volume DABC, 1650 times the volume of the water 
that produced it (compare volume ABCD with small black 
volume D). The pound of ice has now received 327.528 + 
970.4 = 1297.928 B. t. u. and is in a state of steam at atmos- 
pheric pressure and 212° temperature. Any further addi- 
tion of heat to this steam without being- in contact with 
water results in an increase of temperature along- the line 
BK and the steam is said to be superheated. The quantity of 
heat added as superheat is found by multiplying the pounds 
of steam (in this case 1) by the specific heat and by the 
change in temperature. For steam the specific heat varies 
with the pressure. A fair average value is .48. The heat 
absorbed for any degree of superheat may be added to the 
1297.928 B. t. u. thus giving the total heat between the two 
extremes of temperature and pressure selected. Ordinarily 
heating calculations refer only to saturated stcatii, i. e., steam 
in contact with water and superheating need not be con- 
sidered. 

By the use of Equations 3 and 4 and the steam tables 
compare results by filling in the blank table the values for 
steam at 10, 14.7, 50 and 100 pounds absolute pressure. 





Equation | Table 




10 


14.7 


.50 


lOO 


10 


14.7 


50 


100 


Heat of the Liquid 


















Latent Heat 


















Total Heat 



















Three standard tables of properties of saturated steam are 
in general use, Marks and Davis, Peabody, and Goodenough. 
These tables check each other closely and any one may be 
recommended (Table 4, Appendix, is an extract from the 
first table). 

The following summary of directions for the use of any of the 
steam tables gives specific equations for the solution of al- 
most any type of problem using any vapor table. With the 
nomenclature of Marks and Davis, we have: 



24 



HEATING AND VENTILATION 



FOR SUMMATION ABOVE 32° P. 





If Quality 

is 100% 


If Quality 

isX% 


If Superheat is 
D degrees 


Total Heat of 
Formation.... 

Initrinsic Heat 
of Formatiou 

External Work 
of Formation 


H = h + L 
h + I 
{Apu)v 


h + XL 
h + xl 
{xApu)v 


H + CpD 

h -\- I + CpD — (Apu)s 

{Apu)v + iA2ni)s 



FOR SUMMATION ABOVE SOME FEED TEMPERA- 
TURE = t 





If Quality 
is 100% 


If Quality 

isX% 


If Superheat is 
D degrees 


Total Heat of 
Formation 


H~ht or 

h + L — ht 


7i + xL — ht 


h + L -\- CpD — ht 


Intrinsic Heat of 
Formation 


h -r I — ht 


h + xl — Jit 


h + I + CiiD — 
iApu)s — ht 


External Work of 
Formation 


iApu)v 


ixApu)v 


{Apu)v + Upu). 



In these tables the subscript r refers to the condition of 
non-superheats, while the subscript s refers to the condition 
of superheat. In the term Apu, the value of .1 is 1/778, p = 
pressure in pounds per sq. foot and it is the increase in vol- 
ume in cubic feet undergone during- the process in question. 
Some vapor tables, (notably Peabodj^'s) contain columns of 
Apu worked out and tabulated while with the use of other 
tables it is necessary to calculate the values of the Apu terms. 

These tables emphasize those facts the neglect of which 
causes perhaps 90 per cent, of all steam table calculation 
errors, viz: 

X cannot affect, as a factor any steam table value 
except L, I, and (Apu) v. 

The vapor tables are summations above 32° F., and 
for heat summations above any other tempera- 
ture, correction must be made. 

The external work available during formation is in- 
dependent of the feed temperature. 

15. Application of Heat to Gases: — Pressure-volume- 
temperature changes in gases may be found from ideal laws 
which apply with close approximation, or from actual laws 
(modifications of the ideal laws) designed to fit actual con- 
ditions. The ideal laws are much more easily applied and 



APPLICATION OF HEAT TO GASES 25 

give results that are close to average practice; consequently, 
they are used in most engineering calculations. Ideal laws 
are known as (1) The Law of Boyle or of Mariotte, (2) The 
Law of Charles or of Gay Lussac. 

Boyle's Law. — When the temperature of a given loeight of gas 
is maintained constant, the volume and the pressure vary inversely. 
In many pressure-volume applications to gases the tempera- 
ture change is either zero or so small as to be of no serious 
moment. This law applies in such cases. Let P, Pi, P2, 
etc., = absolute pressures in pounds per square foot, and 
y, Ti, >^2, etc., = volumes in cubic feet at the respective 
pressures, then 

FY = Pi Fi = Po Vs, etc. (5) 

In other words, at a constant temperature the product of 
any pressure with its respective volume is a constant quan- 
tity. Thus if 100 cubic feet of air at 14.7 lbs. absolute pres- 
sure be changed to 50 cubic feet without change of tempera- 
ture, the pressure will be (14.7 X 100) ^ 50 = 29.4 lbs. 
absolute, or 14.7 lbs. gage. 

Charles' Law. — When gases are heated, they react ac- 
cording to the Law of Charles; i. e., the volume of a perfect gas 
at constant pressure, or the pressure of a perfect gas at constant 
vohime, is proportional to its absohite temperature. As before 
let P = absolute pressure in pounds per square foot, Y = 
volume in cubic feet, and T = absolute temperature, then 
PY PiFi P2Y2 



etc. (6) 



T Ti T2 

Referring to the first part of the definition of this law, let 
the temperature of a cubic foot of gas (take air for illus- 
tration at atmospheric pressure) be 32° F., if T = 32 -{- 

PY 

460 = 492, P = 14.7 X 144 = 2116.8 and V = 1, then = 

T 
2116.8 X 1 

■ . Now if the temperature of the air is changed to 

492 
some other temperature Ti, say 100° F. at the same pressure, 
PY Pi Fi 

= and, since Pi = P, the new volume is 

T Tx 

2116.8 X 1 560 560 

Yi = • X = = 1.14 y 

492 2116.8 492 

Referring to the second part of the definition of the same 
law, take a cubic foot of air at atmospheric pressure and 
32° F. and change its temperature to 100° F. while the vol- 



26 HEATING AND VENTILATION 

ume remains constant at one cubic foot. Now, the pressures 
at constant volume are proportional to the absolute tem- 
peratures and 

7^ X 1 Pi X 1 



492 560 

Pi = 1.14 P, specific pressure 
Pi = 1.14 J), pounds per square inch. 

General Equation. — The volume occupied by a pound of 
air at any given pressure and temperature (specific volume) 
is the reciprocal of its density at that temperature. At 32° 
F. and atmospheric pressure this is 1 -f- .0807 = 12.391. Sub- 
stituting- 7^1 = (32 + 460), Pi = (14.7 X 144) and Fi = 
12.391, in Equation 6 and reducing- 

PV = 53.3 T (7) 

This is usually written PV = RT, where P is a constant 
which varies for different g-ases. In further study of this 
question, it is found that R represents the foot pounds of 
external work done when the temperature of one pound of 
g-as is raised one deg-ree at constant pressure. For air, as 
found above, it is 53.3. Having- the value R for any g-as and 
any two of the values P, V, or T, the third may be found. 
Note: in Equation 7 P and V must be specific pressure and 
volume, respectively. To illustrate, the pressure of one 
pound of air having- a volume of 5 cubic feet and tempera- 
ture of 100° P. is P = (53.3 X 560) -^ 5 = 5969.6 pounds 
specific pressure, or 41.5 per square inch absolute. Also, 
the volume of a pound of air having- a pressure of 50 pounds 
per square inch absolute and a temperature of 60° is V = 
(53.3 X 520) -^ (64.7 X 144) = 2.97 cubic feet. 

16. Combustion of F«el.s: — Fuels used for heat produc- 
tion are solid, liquid and g-aseous, and contain carbon (O), 
hydrog-en (//), oxyg-en (0), nitrog-en (N), sulphur (8), and 
small amounts of water and ash. In combustion the most 
valuable of all of these constituents are carbon, and hydro- 
g-en. Fuels with hig-h percentag-es of carbon and hydrog-en 
(heat producing- ag-ents) and low percentag-es of ash and 
water are the most desirable. Coal is the universal fuel, 
althoug-h oil and g-as are frequently used. Carbon burns to 
carbon dioxide (CO2) if supplied with sufficient air during- 
combustion or to carbon monoxide (CO) if the air supply is 
restricted. The g-reatest economy is found when 002 is 



COMBUSTION OF FUELS 27 

produced. Hydrogen burns, forming- water, and sulphur 
burns to sulphur dioxide (/S'02). Oxygen in the fuel has the 
same effect as the oxyg-en of the air in supporting- combus- 
tion. Nitrogen has no appreciable chemical action during 
combustion, but it absorbs heat and is thrown away, hence 
it tends to reduce the efficiency of the furnace. Water in 
the fuel has little chemical effect. It absorbs heat in being 
evaporated and superheated and passes off with the gases, 
causing small loss. One pound each of the above elements 
of the coal when completely consumed gives off heat units 
as follows: G to CO2 = 14600, to 00 = 4450, CO to CO2 = 
10150, H to H2O = 62000 (frequently used 52000 to account 
for loss by evaporation and superheating), and 8 to 8O2 = 
4000. 

As an illustration of the chemical changes taking place 
in a furnace when a fuel is raised in temperature suffi- 
ciently high that the combustible unites with the oxygen of 
the air and produces combustion, burn completely one pound 
of coal containing C = .78, H — .04, O = .03, :m = .02, /S = .02, 
H2O = .01, and ash = .10, and note the following points of 
interest: 

(A) Theoretical total heat of the fuel by equation. 

(B) Amount of air needed for complete combustion. 

(a) By analysis, (b) By equation. 

(C) Probable amount of air used for combustion. 

(D) Temperature of the furnace when only the theoret- 

ical amount of air is used for complete combus- 
tion. 

(E) Temperature of the furnace when the probable 

amount of air is passed through the furnace. 

(F) Efficiency of the furnace. 

Theoretical Total Heat of the Fuel (A). — From the hea.t 
values given the following theoretical equation (Du Long's 
formula) has been compiled: 



Total Heat = 14600 C + 52000 (H — ) + 4000 8 (8) 

X 
and when applied to the coal sample as stated gives 

.03 

Total Heat = 14600 X .78 + 52000 X (.04 ) + 

8 
4000 X .02 = 13353 B. t. u. Equation 8 is used when the 
chemical composition of the fuel is known. When this is not 
known, the total heat is found in the laboratory by the use 
of calorimeters. 



28 HEATING AND VENTILATION 

In most furnaces comTyustion is not perfect. Part of the car- 
bon is burned to CO2 giving- off 14600 B. t. u. per pound and 
part to CO giving off 4450 B. t. u. per pound. To find the 
heat value of the coal in such cases use a modification of 
Equation 8. 

Heat liberated = 14600 Ci + 4450 C2 + 52000 
O 

(H — ) + 4000 S (9) 

8 

where Ci and Co = weights of carbon per pound of coal 
burned to COo and CO respectively. Suppose, for illustra- 
tion, that the carbon goes half and half to 002 and CO, then 

the heat liberated is 14600 X .39 + 4450 X .39 + 52000 
.03 

(.04 — ) -j- 4000 X .02 = 9395. Compare this with the 

8 
value obtained by Equation 8. 

Theoretical, Amount of Air Needed for Complete Combus- 
tion (B). — 

(a) Since the atomic weights (relative weights of unit 
volumes referred to H = 1) of C = 12, H = 1, O = 1&, N = 14, 
and S = 32, we have 

12 parts O unite with 32 parts O. (1 lb. O + 2.66 lbs. O = 

3.66 lbs. OO2) 
12 parts unite with 16 parts 0. (1 lb. + 1.33 lbs. = 

2.33 lbs. O) 
2 parts H unite with 16 parts O. (1 lb. H + 8.00 lbs. = 

9.00 lbs. H2O) 
32 parts 8 unite with 32 parts 0. (1 lb. fif + 1.00 lbs. O =: 
2.00 lbs. SOo) 
from which may be found the oxygen required to unite with 
each element for complete combustion. Prom the coal 
analysis, 

.78 X 2.66 = 2.075 lbs. O for the ca.rboTi 
.04 X 8.00 = .320 lbs. O for the hydrogen 
.02 X 1.00 = .020 lbs. O for the sulphur 



Total 2.415 lbs. O per lb. of coal 

Less .030 lbs. O already in the coal 



Net total = 2.385 lbs. O per lb. of coal to be taken 
'from the air. Atmospheric air contains 23 per cent, oxygen 
by weight, hence it will require 2.385 -H .23 = 10.37 pounds 
of air to completely burn the pound of coal if all the oxygen 
of the air is used. If 87 per cent, of the pound of coal is 



COMBUSTION OF FUELS 29 

combustible, then there are needed 10.37 -^ .87 = 11.91 
pounds of air per pound of combustible. 

Where combustion is not perfect the theoretical amount of 
air is not used. Assume as before that the carbon divides 
half and half, then we have 

For Ci, .39 X 2.66 = 1.036 

For €2, .39 X 1.33 = .518 

For H, .04 X 8.00 = .320 

For 8, .02 X 1.00 = .020 



Total 1.894 lbs. O 

Less .030 lbs. O in coal 



Net Total 1.864 lbs. to be taken from 
the air. This makes 1.864 ~ .23 = 8.1 pounds of air per 
pound of coal burned. Compare this value with that for 
perfect combustion. 

(b) The equation usually quoted for the weight of air 
needed for perfect combustion is 

O 

W = 11.52 C + 34.56 (i? ) + 4.32 8 (10) 

8 
which for the assumed coal is TF = 11.52 x .78 + 34.56 
.03 

(.04 ) + 4.32 X .02 = 10.32 pounds. Compare with the 

8 
value by chemical analysis. 

Probable Amount of Air Used for Combustion (C). — There 
can be no exact value placed upon actual amount of air pass- 
ing through a furnace. The construction of the furnace, the 
type of grate used, the depth of the fuel bed, the quality of 
the fuel and the eccentricities of the fireman all influence 
the result. From tests tliat have been conducted upo'ri^vari- 
ous types of heating furnaces under varying conditions of 
service, it seems reasonable to assume that from two to 
three times as much air goes through the average furnace as 
would be needed for perfect combustion. In the most up-to- 
date power plants excess air is reduced to small amounts. 

It is not possible in furnace operation to keep the air 
supply down to the theoretical amount without reducing the 
economy of the furnace. When the fuel bed is thick and the 
air supply reduced, the fuel w^ill receive too small an amount 
of air and carbon will be burned to 00 w^ith a loss of 10150 
B. t. u. per pound. When the fuel bed is thin and the supply 
of air excessive, too much air will pass through the fire 
causing some of the carbon to pass off unburned and carry- 



30 HEATING AND VENTILATION 

ing- away heat unnecessarily by heating the excess air. 
(Read Technical Paper No. 137, Bureau of Mines, Washing- 
ton, D. C.) Of the two alternatives it is better to have too 
much air than not enough, and some of this air should be 
admitted above the fuel bed. To illustrate the economy of, 
excess air in practice, suppose the pound of coal just con- 
sidered is burned in a furnace where the entering air is 60° 
and the stack g-ases are 600°. With the specific heat of the 
gases = .24 we find first, for perfect combustion with 
10.37 + -9 = 11.27 pounds of stack gases, the pound of coal 
has available for boiler use (not counting radiation losses) 
13353 — [11.27 X .24 X (600 — 60)] = 11892.4 B. t. u. 
Second, if there is just enough air to burn the carbon to CO, 
there will be 6.8 pounds of stack gases and 5436 — [6.8 X 
.24 X (600 — 60)] = 4555 B. t. u. available. Third, with 2.5 
times as much air as is theoretically needed and all the car- 
bon burned to CO2, there will be 26.83 pounds of stack gases 
per pound of coal and the heat available w^ill be 13353 — 
[26.83 X .24 X (600 — 60)] = 9875.8 B. t. u. This shows a 
decided advantage in favor of excess air over- a much re- 
stricted supply. Flue gas may be analyzed by the Orsat ap- 
paratus and such analysis used in determining the quality 
of the combustion (See Art. 17). 

Theoketical Temperature of the Furnace (D). — When per- 
fect combustion occurs, the theoretical total heat is g'iven 
off. If it were possible to liberate this heat in a vessel per- 
fectly insulated, all the liberated heat would be used in rais- 
ing the temperature of the gases. The theoretical rise in 
temperature in such an ideal furnace would be 
theoretical total heat (B. t. u.) 



(11) 
pounds of stack gases X specific heat 

Applying to the coal sample above, tr = 13353 -f- (11.27 X 
.24) = 4946° F., and if the air enters at 60°, the temperature 
of the furnace is 4946 + 60 = 5006° F. 

Probable Temperature of the Furnace (E). — Suppose 2.5 
times the theoretical air is used in the furnace, then the 
probable temperature is 

13353 

t = h 60 = 2138° F. 

26.83 X .24 

Radiation and other losses will reduce this value somewhat. 

Efficiency in Furnace Combustion (F). — There are five 

losses in fuel combustion: (a) unburned combustible material 

that drops through the grate with the ash, (b) unburned 



COMBUSTION OF FUELS 31 

hydrocarbon particles that leave the chimney as smoke, (c) 
carbon burned to CO Instead of CO2 by incomplete combus- 
tion, (d) excessive air supply, (e) radiation. These losses 
are apportioned about as follows: 

(a) (Estimated) 1 to 3 per cent, of total heat in coal. 

(b) (Estimated) 1 to 5 per cent, of total heat in coal. 

(c) May vary anywhere between 10 and 50 per cent. 

(d) May vary anywhere between 5 and 15 per cent. 

(e) (Estimated) 2 to 5 per cent. 

It will be seen by this that a large part of the orig-inalheat 
in the coal is not transferred through the heating surface 
of the boiler to the water, but is dissipated through the five 
channels just mentioned. 

Intimately associated with the combustion losses is the 
idea of furnace and holler efficiencies. The most important of 
these are grate efficiency, furnace efficiency and overall 
efficiency. 

Grate efficiency = 

weight (or heat value) of ascending combustible 

(12) 

weight (or heat value) of combustible fired 

If 2 per cent, of the coal drops through the grate, this is 
(100 — 2) -^ 100 = 98 per cent. 
Furnace efficiency = 

heat available for absorption by boiler 

(13) 



heat value of combustible fired 

With perfect combustion of the entire pound of coal and 2.5 
times the required amount of air, this is 9875.8 -^ 13353 = 74 
per cent. If there is a percentage loss through the grate, 
the value 9875.8 will be reduced by this amount. With im- 
perfect combustion, illustrated by the case where the carbon 
divides half and half to CO2 and CO, this is [9395 — 9 X .24 
(600 — 60)] H- 13353 = 61 per cent. If there is a percentage 
loss through the grate, the value 9395 will be reduced by 
this amount. 

heat absorbed by water and steam 

Over-all efficiency = (14) 

heat value of combustible fired 

The heat absorbed by the water and steam is the heat value 



02 


X 


13353 


= 


267.06 


B. 




u. ; 


03 


X 


13353 


■= 


400.59 


B. 




u.; 


20 


X 


13353 


=z 


2670.60 


B. 




u.; 


10 


X 


13353 


= 


1335.30 


B. 




u. ; 


02 


X 


13353 


= 


267.06 


B. 




u.; 










4940.61 


B. 




u.; 


(13353 — 4940.61) -^ 13353 


= 



32 HEATING AND VENTILATION 

of the combustible less all the losses. Suppose the losses in 
the sample are: 

through the grate, 

unburned carbon (smoke), 

imperfect combustion, 

excessive air supply, 

radiation, 

total losses, 
then the over-all efficiency is (13353 
63 per cent. When the word efficiency is mentioned in con- 
nection with small power and heating plants, the over-all 
efficiency is understood unless otherwise specified. The effi- 
ciency of the average boiler is 60 to 65 per cent., but efficien- 
cies as high as 75 per cent, may be found in continuous 
service in some of the better plants (For boiler operation, 
see Arts. 87 and 187). 

17. Flue Gas Analysis. — The quality of the fuel combus- 
tion in many plants is determined by the Orsat, or similar 
apparatus, which is used in obtaining an analysis of the flue 
gases by volume as they leave the boiler. Values are found 
for CO2, CO and O. The CO2 varies from 6 to 17 per cent, of 
the total volume of the flue gases. Between 10 and 13 per 
cent, is considered good practice. CO is always found in 
small quantities, say from to .5 per cent. When excess air 
is less than 25 per cent., CO is probably forming in prohibi- 
tive amounts. With good combustion and 100 per cent, excess 
air (good boiler practice), there should be but a trace of CO. 
Free oxygen is always found where there is an excess of 
air. This percentage of O (0 to 15 per cent.) may be used to 
determine the amount of excess air. 

Of the three determinations made by the use of the 
Orsat apparatus, the CO2 and O determinations are consid- 
ered of greatest value. When carbon and oxygen unite to 
form carbon dioxide gas, it is found that with the same tem- 
perature and pressure the carbon dioxide occupies the same volume 
as the oxygen entering into the combination. Assuming perfect 
combustion (no carbon monoxide) and just enough air to 
supply the oxygen, the resulting gas volumes will be 21 per 
cent. CO2 and 79 per cent. N. A test with the Orsat in this 
case should show 21 per cent. CO2, per cent. CO, and per 
cent. O. Again, assuming perfect combustion and an excess 
of air (say 100 per cent.), one-half of the oxygen of the air 
is used for the CO2 and the Orsat should show 10.5 per cent. 



FLUE GAS ANALYSIS 33 

CO2, 10.5 per cent. O, and per cent. CO. That is to say, the 
sum of the COo and percentages will be 21 per cent., the same 
as the original oxygen volume. Again, assuming imperfect 
combustion and a certain amount of CO, it is found that 
loith the same temperature and pressure the carbon monoxide occu- 
pies ticice the volume of the oxygen entering into the combination 
and the resulting stack gases have a larger volume than the 
entering air by one-half of the percentage of CO present. 
With high percentages of CO this change in volume would 
need to be taken into account. In all ordinary cases, how- 
ever, it is satisfactory to consider the stack gases as 79 per 
cent. X and the remaining 21 per cent, composed of CO2, CO 
and O. 21 per cent. CO.2 shows the highest possible efficiency, 
i. e., no excess air and perfect combustion. This is never 
obtained in practice. Any value of C'Oo less than this indi- 
cates (1) excess of air, if no CO is present; (2) deficiency of 
air, if CO is present and no 0; (3) improper mixture in the 
combustion chamber, if both CO and O are present. 

Computations to find the relation hetioeen tveights of flue gas 
and entering air are sometimes complicated by the necessity 
of changing from weights to volumes and vice versa. Vol- 
ume readings of the Orsat are generally used directly in 
terms of the densities of the gases since, as above stated, 
equal volumes of the gases at the same temperature and 
pressure contain the same number of molecules. Use the 
equations ^^ ^^^ _|, 32 o. + 28 (CO + 2V) 

W = X Oi (15) 

12 (CO 2 + CO) 

Where W = weight of flue gas in pounds per pound of coal, 
C'l =z percentage of carbon in the coal, and the other symbols 
represent percentages of each as shown by the Orsat. N is 
found by differences i. e., 100 — (COo + CO + 0). For infor- 
mation on the use of the Orsat apparatus see very excellent 
explanation in "Coal," hy Somermeier. 

Application (1). — Coal, having a composition as stated 
in Art. 16, is being burned in a furnace without loss through 
the grate. Samples of the flue gas show 12 per cent. CO2 
and 9 per cent. O. What is the weight of flue gases per 
pound of coal burned? Compare this value with the the- 
oretical amount of air as in Art. 16 (B) and note the excess 
supplied. From Equation 15 

44 X 12 + 32 X 9 + 28 X 79 

W = X .78 = 16.4 

12 (12 + 0) 



34 HEATING AND VENTILATION 

Excess air = 16.4 — 10.37 = 6.03 pounds. Where a grate 
loss is known to exist, Ci should be corrected by this 
amount. Thus for a 2 per cent, loss, Ci = .98 X .78 = .764. 
Application (2). — Coal as in application (1); 2 per cent, 
loss through the grate; 8 per cent. COo; 12.5 per cent. O; .5 per 
cent. CO. Find the weight of stack gases and excess air per 
pound of coal. 

44 X 8 + 32 X 12.5 -|- 28 (.5 + 79) 

* W = ■ X .764 — 22.3 

12 (8 + .5) 

Excess air = 22.3 — 10.37 = 11.93. 



CHAPTER II. 



AIR COMPOSITION — VENTILATION — HUMIDITY — DRAFT. 



18. Composition of Atmospheric Air: — The subject of 
ventilation in its relation to health should be introduced by 
a brief consideration of the properties of the air supplied. 
Air is a very important factor in building economy. In addi- 
tion to its value as a heating- medium it determines in a 
marked degree the health of the occupants of the building. 

The human body may be considered a "well equipped and 
very complex power plant. As the carbon, hydrogen, and 
oxygen in the fuel and air supply in any mechanical power 
plant are consumed in the furnace, the resulting heat ab- 
sorbed in the generating system and finally turned into 
work through the attached mechanisms; so the human body 
absorbs heat from the combustion of food and turns it into 
work. The products of combustion in both cases are largely 
carbon dioxide and water. The chief requisites of the 
mechanical plant are good fuel, well regulated draft and 
efficient stoking. Similarly, the human body needs good 
food, pure air and healthful exercise. Of the three require- 
ments all are of the utmost importance, but the second has 
probably the greatest significance, since no person can long 
keep in health with impure air, even with the best of food 
and a sufficient amount of exercise. 

In its simplest analysis air is made up of two elements, 
oxygen and nitrogen, in the volume ratio of 20.9 to 79.1 and 
a density ratio of 23.1 to 76.9, respectively. In a complete 
analysis of pure air a number of other elements and com- 
pounds are found, making a mechanical mixture that is 
somewhat complex. Most air samples show traces of carbon 
monoxide, hydrogen sulphide, ozone, argon, compounds of 
ammonia, and compounds of nitric, nitrous, sulphuric and 
sulphurous acids. The heating and ventilating engineer, 
however, is interested chiefly in the amount of oxygen, 
moisture and carbon dioxide present. Air taken from the 
open country and not contaminated with the poisonous gases 
or the dus<" and refuse from cities has the following com- 



36 HEATING AND VENTILATION 

position according- to Professor Carpenter, Heating and 
Ventilating Buildings (See also Encyclopedia Britannica, 
Respiration). 

Oxygen Per cent, of volume 20.26 

Nitrogen " " " 78.00 

Moisture " " " 1.70 

Carbon dioxide " " " .04 

These values are fairly constant, except that of the moisture 

which may vary from 0+ to 4 per cent, of the entire weight 

of the air. 

Experiments have shown that normally pure air in the 
process of respiration when exhaled from the lungs of the 
average person has 

Oxygen Per cent, of volume 16 

Nitrogen " " " 75 

Moisture " " " 5 

Carbon dioxide " " " 4 

Comparing these values with those for pure air, oxygen is 
reduced one-fifth, nitrogen is reduced one twenty-fifth, vapor 
is increased three times and carbon dioxide is increased one 
hundred times. Oxygen has been consumed in its union with 
the excess carbon and hydrogen in the human body and is 
given off as carbon dioxide and water vapor. It may be 
seen from these ratios, that the gradual reduction of the 
oxygen content and the very rapid increase of CO2 w^ith its 
accompanying impurities soon render unfit for use t,he air 
in any building occupied by a number of people.. To avoid 
this state of affairs, fresh air should be supplied continu- 
ously and at such points as will provide the most uniform 
circulation. 

19. Oxygen and Nitrogen: — Oxygen fills about one-fifth 
of the volume in atmospheric air and is the element that 
makes combustion possible. The other four-fifths of the 
space is filled with nitrogen. In a providential way this 
nitrogen acts with the oxygen to control the rapidity with 
which combustion takes place. Nitrogen seems to have little 
effect upon respiration, except to retard chemical action. If 
one were to attempt to live in an atmosphere of pure oxy- 
gen, the chemical action taking place through the lungs 
would be so rapid that the human body would not be able 
to maintain it. 

20. Carbon Dioxide; — The amount of COo in the air is 
used as an index to the purity of the air. It is not consid- 



COMPOSITION OF AIR 37 

ered a poisonous gas. It has slight taste and odor, but no 
color. It is found in many natural ^waters and manufac- 
tured beverages, the chief one being "soda water," which is 
made by forcing carbon dioxide into water under pressure. 
The real action of CO2 when taken into the lungs is not well 
known. It has the effect of producing physical depression 
and where found in sufficient quantity will even cause death 
by suffocation, very similar to submergence in water. What- 
ever its effect upon human life may be, its presence in any 
room used for habitation (assuming no open fires or gas jets 
in the room) is an indication of the lack of oxygen and an 
excess of impurities thrown off by respiration. Good coun- 
try air has 4 parts CO2 in 10000 parts of air and room air 
should never be allowed to have more than 8 to 10 parts in 
10000 parts of air. It becomes the duty of the heating engi- 
neer therefore to provide pure air in sufficient quantities, to 
enter and withdraw the air from the room in a manner such 
as will not be uncomfortable to the occupants and to keep 
the air fairly uniform in quality throughout the room. Car- 
bon dioxide is 52 per cent, heavier than air of the same tem- 
perature and therefore has a tendency to fall. Exhaled air, 
however, has excessive moisture, has a temperature much 
higher than that of the room air and is 2 to 3 per cent, 
lighter than when inhaled. Its tendency to rise neutralizes 
the excessive density of the CO2, and as long as the air is 
absolutely quiet, results in a fair diffusion throughout the 
room air. In large audience rooms the heat given off from 
the occupants is sufficient to cause strong currents which 
carry this impure air to the upper part of the room. A care- 
ful study of the physical conditions within inhabited rooms 
shows that the location of the Mel air zone may be anywhere 
from the floor to the ceiling, depending upon the room vol- 
ume (large or small respectively) allowed per inhabitant 
and the rapidity of air movement in the room. In investi- 
gating air conditions, tests for OOo should be made in all 
sections of the room. Tests conducted at the breathing line 
represent living conditions for the inhabitants. In residence 
work air is usually entered and withdrawn at the .floor line. 
In large plants where the air circulates by mechanical 
means, it usually enters above the heads of the occupants 
and is withdrawn at the floor line. Some engineers advo- 
cate the updraft system with the air entering near the floor 
and leaVing at the ceiling. In the latter case ventilation is 
simplified but heating is made very expensive. 



38 



HEATING AND VENTILATION 



A method of determining the percentage of carhon dioxide in 
the air, based upon the fact that barium carbonate is nearly- 
insoluble in -water, may be performed as follows: provide 
eleven bottles with rubber stoppers having- two holes each 
and connect them continuously by glass and rubber tubing-, 
so that if suction be applied at the first bottle of the series 
air will be drawn in at the last of the series and the same 
air will be passed through all. In this way a sample of the 
air to be tested may be drawn into each bottle. The capac- 
ities of the bottles in ounces must be respectively, 23%, 18i/4. 
16%, 14, 9%, 7%, 5%, 4, 314, 2% and 2. These may readily 
be prepared by partially filling with paraffin. Into each 
bottle is then placed % ounce of a 50 per cent, saturated 
solution of barium hydrate (Ba(OH)2). Air to be tested 
is drawn through the system until all the bottles contain a 
fair sample. Each bottle is then thoroughly shaken, so that 
the liquid may be brought into good contact with the air 
sample. If the least turbidity or cloudiness appears it indi- 
cates 

First or largest bottle, 0.04 per cent. 

Second bottle. 



CO, 



Third 

Fourth 

Fifth 

Sixth 

Seventh 

Eighth 

Ninth 

Tenth 

Eleventh 



0.06 
0.07 
0.08 
0.10 
0.15 
0.20 
0.30 
0.40 
0.60 
0.90 



The glass tubes should extend no farther than the bottom 
of the stoppers. Fig. 4, a, shows four of the bottles and 



r\r\ 



J 




(a) 



Fig. 4. 



(b) 



COMPOSITION OF AIR 39 

their connections. To illustrate, suppose that the air of a 
room was tested and that in -the first, second, third, fourth, 
fifth and sixth bottles the liquid became turbid after vigor- 
ous shaking-. Such room air would have contained 0.15 per 
cent, carbon dioxide and would have been considered quite 
unfit for breathing. 

A second, less cumhersome method of testing for the per- 
centage of carbon dioxide is shown in Fig. 4, 6. A bottle of 
about 6 ounces capacity is fitted with a rubber stopper hav- 
ing two holes. Through one hole a glass tube is brought 
from the bottom of the bottle and to the outer end of this 
tube is connected a valved bulb similar to those found on 
atomizers. Into the bottle are placed 10 cubic centimeters 
of a solution made by dissolving .53 gram of anhydrous 
sodium carbonate (NooCOz) in 5 liters of water and adding 
.01 gram of phenolphthalein. The water used must have 
been previously boiled for at least one hour in an open ves- 
sel. With the apparatus so prepared, squeeze the bulb, thus 
forcing air from the room through the liquid and into the 
bottle. The open hole in the rubber stopper is then closed 
with the thumb and the bottle vigorously shaken. Then 
another bulb full of air is injected and the bottle again 
shaken. This process is continued and the number of bulbs 
of air noted until the red color of the solution, due to the 
phenolphthalein, disappears. This number of bulb fillings 
when referred to a table (Similar to Table II) prepared for 
this particular apparatus, is indicative of the purity of the 
air. After such an apparatus is completed it must be cali- 
brated before being used. This is done by obtaining the 
number of bulb fillings of pure country air necessary to clear 
the liquid, which will usually vary from 40 to 70. The table 
for use with this special apparatus may be obtained by pro- 
portion from Table II, in which the number of bulb fillings 
of country air is 48. If now with the new apparatus it is 
found that 60 bulb fillings are required to clear the liquid, 
the proportionate table would be made by multiplying the 
number of bulb fillings given below by the ratio of 60 -^ 48, 
or 5 to 4. It is important that the bulb be compressed the 
same amount for each filling, and that the shaking of the 
bottle and contents be continued the same length of time 
after each filling, to obtain uniform results. The Wolpert 
Air Tester, a commercial apparatus, may be obtained for 
this line of testing. 



40 HEATING AND VENTILATION 

TABLE II. 



Fillings 


Per cent. CO2 


Filling-s 


Per cent. CO2 


48 


.030 


15 


.074 


40 


.038 


14 


.077 


35 


.042 


13 


.080 


30 


.048 


12 


.083 


28 


.049 


11 


.087 


26 


.051 


10 


.090 


24 


.054 


9 


.100 


22 


.058 


8 


.115 


20 


.062 


7 


.135 


19 


.064 


6 


,155 


18 


.066 


5 


. .180 


17 


.069 


4 


.210 


16 


.071 


3 


.250 



The methods just mentioned for determining- CO2 are 
fairly satisfactory in obtaining- quantitative values from 
which the quality of the ventilating air in any system may 
be judged. If exact percentages of CO, CO2, and IS! are re- 
quired, the Pettersson-Palmquist, the Orsat, or similar ap- 
paratus must be employed. For descriptions of these see 
Stillmans' Engineering Chemistry, Carpenter's Heating and 
Ventilating Buildings, Hempel's Gas Analysis, translated by 
Dennis, Abady's Gas Analyst's Manual, and Somermeier's 
Coal. 

31. Amount of Fresh Air Needed per Person: — The need 
of a continuous supply of fresh air in residences and busi- 
ness hoiises can scarcely be overestimated. Health is the 
greatest of all blessings and pure air is essential to health. The 
most convincing argument that can be presented on this 
point is an analysis of the vital statistics of the country 
covering a large number of years. Persons afflicted with 
respiratory diseases are recommended by the medical fra- 
ternity to seek a high, dry, sunny climate and live in the 
open air. The rarefied atmosphere causes continuous deep 
breathing, which exercise in itself has a tendency toward 
strengthening the afciicted parts and throwing off disease, 
and the dry air probably serves the lung tissue as a cleanser 
as the blotter does the page of wet ink. These condi- 
tions, in connection with the sunshine which is one of our 



AIR REQUIRED PER PERSON 41 

best germicides, form the only known remedy for combating- 
such diseases. It is a safe conclusion that the element of 
pure air which enters so largely into the overcoming of the 
disease, once it is contracted, is one of the best preventives 
as well. Statements are made (occasionally in the technical 
press) that respired air is not harmful and that satisfactory 
ventilation may be had in inhabited rooms with much less 
fresh air than that usually allowed. The first of these two 
statements has never been proved. On the contrary the cir- 
cumstantial evidence of the impurity of respired air is fairly 
conclusive. The second may be true for ventilating systems 
where the air supply is subdivided into small amounts and 
carried directly to the person (See experiments by Professor 
Bass at University of Minnesota, Trans. A. S. H. & V. E., 
Vol. XIX, p. 328). Applications such as this, however, can 
not be regarded as touching general practice. 

The average adult, when engaged in ordinary indoor 
occupations, will exhale about 20 cubic inches of air per 
respiration. He will also have 16 to 24 respirations per 
minute, totaling 400 + cubic inches or, say .25 cubic foot of 
air per minute. Allowing 4 per cent. CO2 in respired air the 
average person will exhale 60 X .25 X .04 = .6 cubic foot 
CO2 per hour. This is constantly being diffused throughout 
the air of the room. If the carbon dioxide and other impur- 
ities could be disassociated from the rest of the air and ex- 
pelled from the room without taking large quantities of 
otherwise pure air with them, the problems of the heating 
and ventilating engineer would be simplified, but this cannot 
be done. Rapid difEusion of respired air throughout the room 
renders it necessary to dilute the room air with fresh air in 
order that the purity may be maintained at a safe value. 
Ideal conditions are found when interior air is as pure and 
refreshing as that of the open country, but the mechanical 
difficulties around such a ventilating system would be so 
great as to render it prohibitive. The standard of purity 
which should be aimed at, and which may be obtained with 
a first-class system, is .06 of one per cent. CO2, i. e., 6 parts 
of CO2 in 10000 parts of air. Systems maintaining constant 
ventilation at 8 parts in 10000 are considered satisfactory. 
Stated in a simple form for calculation, let Q' = cubic feet 
of atmospheric air needed per hour per person, A = cubic 
feet of CO2 given off per hour per person, n = standard of 
purity to be maintained (allowable parts of CO2. in 10000 



42 HEATING AND VENTILATION 

parts of air), and /> = standard of purity in atmospheric 

air, say 4; then 

-1 

Q' = (16) 

n — p 
To maintain constant ventilation at 7 parts COa in 10000 
parts of air, with pure air at 4 parts in 10000, we have Q' = 
.6 -T- (.0007 — .0004) =: 2000 cubic feet of air per hour. Based 
upon .6 cubic foot of CO2 exhaled per person per hour. Table 
III g-ives the amount of air needed to maintain constant ven- 
tilation at the various standards of purity. 
TABLE III. 
Cubic Feet of Air per Person per Hour. 



n 


A 


Q 


6 


.6 


3000 


7 


.6 


2000 


8 


.6 


1500 


9 


.6 


1200 


10 


.6 


1000 



It should be understood that no hard and fast rule can 
be given for the air requirement per person. This varies 
with the physical development and occupation of the indi- 
vidual, but it varies in a greater degree with the state of 
the person's health and the sanitary value of his surround- 
ings. In general, the average adult subjected to average in- 
door conditions requires 1800 enhic feet of fresh outdoor air per 
hour. Stated as an equation, the amount of air needed for 
ventilation is Q' = ISOO X, where X = the number of people 
to be provided for. 

The aniounts of air in cubic feet per person per hour 
given in Table IV, may be considered good practice for the 
various classes of service. 

TABLE IV. 



Hospitals. Ordinary 


2000-2500 


" Surgery 


2500-3000 


" Epidemic 


5000-6000 


Workshops. Ordinary 


1800-2000 


Unhealthy trades 


3000-3500 


Schools, Offices. Prisons 


1800 


Theaters and Assembly Halls 


1400-1800 



VENTILATION 43 

One ordinary gas flame of 16 to 20 candle power, using 
4 to 5 cubic feet of gas per hour, will vitiate as much air as 
four or five people. Where many open flame gas lamps are 
used, this fact should be taken into account. 

22. Ventilation: — Ventilation is the art of maintaining in- 
terior atmospheres at a comfortable temperature and humidity, and 
a purity approaching that of open country air. Such a standard 
may be regarded absolutely safe by any one. To accomplish 
this, large amounts of fresh air should be introduced to the 
building and distributed so the occupants will not be sub- 
jected to unpleasant drafts. Fans placed in the rooms to 
circulate the air make the room atmosphere more habitable 
on a warm day, but this process should not be mistaken for 
ventilation. The mere process of fanning the air does not purify it. 

Air may be tested for bacteria and micro-organisms by 
exposing specially prepared gelatine plates or tubes to the 
air of a room a certain length of time, say five or ten min- 
utes, permitting the organisms to germinate and counting 
the colonies. (See Report of Ventilation Division, Chicago 
Health Dept., Page 57, Vol. XX. Trans. A. S. H. & V. E.) 
Such tests are most satisfactory but require considerable 
care in application and are not generally used. The CO2 
test mentioned in Art. 20, while not a direct equivalent, is 
simpler and is generally employed. In testing the qiiality 
of room air by any method it is well to call attention to the 
fact that the ordinary running conditions of any room can- 
not absolutely be determined by a single test. Trials should 
frequently be made and records kept. Upon one day atmos- 
pheric conditions may be favorable and tests may show a 
small amount of impurity. On other days when the condi- 
tions are not as favorable impurities may be found in large 
quantities even though running conditions seem to be dupli- 
cated. Further, if the only requirement governing the ven- 
tilation of buildings is that a satisfactory CO2 test be 
passed, there is great danger of overrating or underrating 
the ventilating system of the building. A safe method in rat- 
ing ventilating systems is to require a minimum air supply in addi- 
tion to a maximum permissible percentage, of CO2 at the breathing 
line. For further study of this subject, see recommendations 
by the American Society of Heating and Ventilating Engi- 
neers, Jour. Apr. 1916, p. 91. Also Trans. A. S. H. & V. E.. 
Vol. XXII, p. 43. 

23. Air Purification: — Air contains dust, fine particles 
of mineral and animal matter, bacteria, and micro-organisms 



44 HEATING AND VENTILATION 

held in mechanical suspension. The more heavily charged 
with these impurities ventilating air becomes, the more dan- 
gerous it is to the human system. Most materials held in 
mechanical suspension may be removed by filtering (passing 
through fine cloth screens) or by washing (passing through 
films or sprays of water). Filtering and washing systems 
are beneficial in all cases and are necessities in many. Fil- 
ters cost less to install and operate, but they occupy larger 
transverse areas and are not as effective as the washing 
systems. Washing air removes most of the mechanically 
suspended particles but it does not necessarily eliminate 
chemical impurities, bacteria and the like. The location of 
the air supply intake to a building carries with it a great re- 
sponsibility. Air supplied to a building should always be 
taken from the purest source possible, and when this supply 
is known to be bad it should be thoroughly washed before 
sending through the ventilating system. 

RErERENCES. — Trans. A. S. H. & Y. E. Studies in Air Clean- 
liness, Vol. XXI, p. 211. The Problem of City Dust, Vol. XXI, 
p. 225. 

Ozone is considered by some to be effective as an air 
purifier. It is an unstable form of oxygen probably contain- 
ing a greater number of atoms per molecule and is formed 
by passing air through a highly charged electrical field. Be- 
cause of its instability as a substance, it readily breaks up 
and becomes more active as an oxidizing agent than oxygen 
itself. In its decomposition a part becomes oxygen and the 
balance is said to enter into combination with substances in 
the air, thus cleansing the air from these substances. 
Two claims are made for ozone. The first is that it is a puri- 
fier, the second that it is a deodorizer. The first has not been 
proved satisfactorily, but the second is substantiated by 
many proofs. Ozone without doubt conceals odors, but it is 
not known if the substances producing the odors are ren- 
dered harmless to the human body. 

References. — Trans. A. S, H. & V., E. An Experiment with 
Ozone as an Adjunct to Artificial Ventilation at the Mt. Sinai 
Hospital, N. Y. C, Vol. XXI, p. 256. Air Ozonation, Vol. XX, 
p. 337. Ozone and Its Applications, Vol. XIX, p. 128. H. & Y. 
Mag., Ozone, July, 1914, p. 16. 

24. Moisture w^ith Air: — Moisture in the atmosphere 
affects the comfort of the occupants as well as the efficiency 
of the heating and ventilating system in any room. With 



HUMIDITY 45 

moisture in the room a person may feel comfortable when 
the temperature is several degrees lower than the comfort- 
able temperature of dry air. A dry atmosphere takes up 
moisture from the room furnishings and from the skin sur- 
face of the occupants. The vaporization of moisture from 
the skin causes a loss of heat from the body and gives to 
the person a sense of cold which is relieved only when the 
temperature of the room is increased. An atmosphere that 
is fairly saturated with moisture demands little evaporation 
from the skin, in which case the body retains its heat and 
the person has a sensation of warmth which is relieved only 
by lowering the temperature of the air of the._room. At low 
temperatures moisture in the atmosphere chills the surface 
of the skin by actual contact. This is not as noticeable 
when the air is dry. It follows from the above statements 
that the range of comfortable temperatures is less for moist 




30 32 34 3(5 35 40 42 44 A6 48 50 5Z 54 56 58 60 62 64 66 68 70 72 74 76 78 

RELATIVE HUMIDITY 
Fig. 5. 



air than for dry air. The Chicago Commission on "Ventila- 
tion, under the direction of Dr. E. Vernon Hill, developed a 
series of curves from a large number of tests, showing the 
best relation between the relative humidity and the comfort- 
able temperature in a room (See Trans. A. S. H. & V. E., page 
607, Vol. XXIII). The curves in Fig. 5, are plotted from a 
summary of these tests. It will be noted that the condition 
represented by 65° and 55 per cent, humidity is as satisfac- 
tory as that of 70° and 35 per cent, humidity. 



46 



HEATING AND VENTILATION 



In addition to its effects upon the human body, moisture 
in the atmosphere has the quality of storing- convected heat. 
It is thus a better heat carrier than dry air and is a benefit 
to the heating- and ventilating- system in any building-. 

References.— ff. £ V, Mag. The Primary Physiolog-ical 
Purpose of Ventilation, Sept. 1913, p. 35. Metal Worker. 
Humidity and House Sanitation Explained, Jan. 24, 1913, p. 
159. Trans. A. 8. H. & Y. E. The Recirculating- of Air in a 
School Room in Minneapolis, Vol. XXI, p. 109. Relative 
Humidity, Vol. XVIII, p. 106. 

25. Humidity:— A &so7i<te humidity is the 
amount of moisture mixed with the air at 
any temperature, expressed in g-rains or in 
pounds per cubic foot. Relative humidity is 
the ratio of the amount of moisture actu- 
ally with the air divided by the amount of 
moisture which the same volume could 
hold at the same temperature when satu- 
rated. The temperature of any air at 100 
per cent, saturation (100 per cent, relative 
humidity) is called the dew point. Relative 
humidity is obtained by using wet-and-dry 
bulb thermometers or by any one of a num- 
ber of hyg-rometers supplied by the trade. 
The wet-and-dry bulb hygrometer has a 
very simple application and is generally 
used. Having g-iven two thermometers 
(Fig-. 6) let one register the temperature of 
the room air and the other, kept wet by a cloth which covers 
the bulb and projects into a vessel filled with water, a tem- 
perature below that of the room air. If the air is saturated 
the two thermometers will record the same temperature. If 
the air is not saturated the thermometer readings will differ 
according- to the humidity. It will be readily seen that the 
lowering of the mercury in the wet thermometer is due to the 
extraction of the heat from the mercury column in vaporiz- 
ing- the moisture from the bulb to the air. 

In taking readings, let the mercury find a constant level 
in each thermometer and note the difference in temperature, 
between the two. In Table 12, Appendix, at this difference 





/T\ 


■ --— " -■ — ^ 




"%' 


? 


pia ' 




M 


1 


-110 . 




lOCH 


o 


-100 




90- 


J0 




-90 ' 




BC. I 




• 


■eo 




70. |~- 






-10 




, 60- 
ISO- 
4^ 
30- 
20- 


1? • 


fc: 


-60 ; 

-50 

■io 

-20 ' 




: 


N 




-lO ', 
-0 ] 


I 


tjj 


i 










'-^ - ■:a 



Fig-. 6. 



HUMIDITY 



47 



and at the room temperature read off the relative humidity. 
Having found the relative humidity take from Table 13, 
Appendix, the amount of moisture with saturated air at the 
temperature recorded by the dry thermometer (absolute 
humidity at saturation). Multiply this by the relative 
humidity found and the result is the absolute humidity at 
the given relative humidity, i. e., the actual amount of 
moisture with the air per cubic foot of volume. 




Fig. 7. 



Application. — Room air, 70°; difference in readings, 6°. 
From Table 12, the humidity is 72 per cent. From Table 13, 
col. 7, .72 X .001153 = .00083 pounds (5.81 grains) per cubic 
foot. 

Instruments have been designed giving the relative 
humidity by graphical charts. Fig. 7, commonly known as 
the hygrodeik, shows such an instrument. To find the rela- 
tive humidity swing the index hand to the left of the chart 
and adjust the sliding pointer to that degree of the wet 



48 



HEATING AND VENTILATION 



bulb thermometer scale at which the mercury stands. Swing 
the index hand to the right until the sliding pointer inter- 
sects the curved line extending down- 
ward to the left from the degree of the 
dry bulb thermometer scale indicated 
by the top of the mercury column in 
the dry bulb tube. At that intersection 
the index hand will point to the rela- 
tive humidity on the scale at the bot- 
tom of the chart. Should the tempera- 
ture indicated by the wet bulb ther- 
mometer be 60° and that of the dry 
bulb 70°, the index hand will indicate 
a humidity of 55 per cent, when the 
pointer rests on the intersection of the 
60° wet bulb and 70° dry bulb lines. 

The instrument in most general use 
for humidity determinations is the 
Sling Psychrometer (See Fig. 8). This 
is a wet-and-dry bulb outfit pivoted to 
a handle in such a way that the ther- 
mometers may be revolved through the 
air thus causing a circulation of air 
over them The wet bulb projects 
beyond the dry bulb and is covered with a fine mesh 
cloth. This cloth is dipped into distilled water and the ap- 
paratus revolved. Read the mercury level frequently and 
note the reading of each thermometer at the time the mer- 
cury in the wet bulb is at its lowest level. For accurate work 
the thermometers should meet a current of air of approximately 15 
feet per second, according to government recommendation. 

Table 12, Appendix, represents U. S. Weather Bureau 
Standards and is used as a reference in this book. Experi- 
ments by Mr. Willis H. Carrier, presented in a paper to the 
American Society of Mechanical Engineers in 1911, show 
humidities differing somewhat from Table 12 (See "Psychro- 
metric Charts" following Table 14, Appendix). 

26. Humidity Chart:— For close approximations the 
humidity chart (Fig. 9) may be used in determining relative 
humidity, absolute humidity, dew point, temperature of wet . 
bulb and temperature of dry bulb. On the left of the chart 




Fig 



HUMIDITY DETERMINATION 



49 



HYGROMETRIC CHART 




10 20 30 40 50 60 70 80 • 90 100 

RELATIVE HUMIDITY IN PER CENT 



Fig-. 9. 



Note. — Fig. 9 represents two charts in one. First : the dry bulb 
temperature curve, which drops to the left, unites with the wet bulb 
and relative humidity coordinates. Second : the absolute humidity 
curve, which rises to the left, unites with the dry bulb and relative 
humidity coordinates. This makes it possible to use the two charts as 
one, through the relative humidity scale which is common to both. 



50 HEATING AND VENTILATION 

is a scale referring to horizontal lines giving temperatures 
of the wet bulb. The scale on the right, referring to the 
lines curving downward from right to left, is the tempera- 
ture scale of the room, or dry bulb temperature. The scale 
along the bottom of the chart gives the relative humidity. 
The scale of numbers up the center of the chart refers to 
the lines curving downward from left to right and indicates 
absolute humidity. For illustration, assume a dry bulb tem- 
perature of 70° and a wet bulb temperature 60°, and find 
relative humidity, absolute humidity and temperature of the 
dew point. Starting on the right hand scale at 70, follow 
down the room temperature curve until it crosses the hori- 
zontal line of 60° wet bulb temperature. From this intersec- 
tion drop to the relative humidity scale and read there 55 
per cent. To obtain the absolute humidity trace up the rela- 
tive humidity line to its intersection with the 70° abscissae 
(horizontal line through 70°) and obtain 4.4 grains per cubic 
foot. If the room air should drop in temperature, the abso- 
lute humidity would remain the same until the dew point is 
reached (neglecting air contractions). Tracing down the 
4.4 ^rain line to 100 per cent, relative humidity gives the 
room temperature 52°. This shows that if so cooled the air 
begins depositing moisture at this temperature. If the tem* 
perature of the room air should increase to 90°, the relative 
humidity may be obtained by following the 4.4 grain line to 
its intersection with the 90° abscissae line of room tempera- 
ture and from this intersection dropping to the relative 
humidity scale at 31 per cent. Thus, having air under any 
set of temperature and humidity conditions, the effect that 
a change in any one condition would have upon the others 
may be obtained without calculations. 

Application 1. — The air of a room gives a dry bulb read- 
ing of 80° and a wet bulb reading of 69°. What is the rela- 
tive humidity? 

Solution. — Find intersection of dry bulb curve and wet^ 
bulb abscissae. From such intersection drop perpendicular to 
relative humidity scale and read 57.5 per cent. Check by 
Table 12, Appendix: 80° room temperature and 11 degrees 
difference gives 57 per cent, relative humidity. 

Application 2. — In the above problem determine the num- 
ber of pounds of water vapor in the room if its capacity is 
3500 cubic feet? 



HUMIDITY DETERMINATION 51 

Solution. — At the intersection of the 80° and 58 per cent. 
coordinates, read absolute humidity in grains of moisture per 
cubic foot as 6.2. Total moisture in room = 3500 X 6.2 = 
21700 g-rains, or 21700 -^ 7000 = 3.1 pounds of water in form 
of vapor. Check by Table 13, Appendix. From this table, 
column 7, the weight of the vapor in pounds present at 
saturation at 80° is by interpolation, .001578 per cu. ft. At 57 
per cent relative humidity each cubic foot would contain 
.001578 X .57 = .000899 pound and 3500 cubic feet would con- 
tain 3.15 pounds. 

Application 3. — To what temperature could this room be 
cooled before moisture would be deposited from the air, i. e., 
at what temperature of the air would the dew point be 
reached? 

Solution. — The dew point for this room air is the tem- 
perature at which 6.2 grains of moisture per cubic foot rep- 
resents saturation, or 100 per cent, relative humidity. There- 
fore follow the 6.2 g^rain line to intersection with the 100 
per cent, vertical and read 63°. Check by Table 11, Appendix. 
Temperature at which 6.2 grains moisture becomes the sat- 
uration quantity is by interpolation, 62.3°. 

Application 4. — To what temperature could this room be 
heated without moisture addition or loss and maintain a 
relative humidity of not less than 50 per cent? 

Solution. — Following- the 6.2 grain line to intersection 
with 50 per cent, ordinate, read from the right the room tem- 
perature, 85°. Check by Table 11, Appendix. Since 6.2 
grains at the temperature sought will be 50 per cent, of the 
moisture of saturation at that temperature, 12.4 grains 
would be saturation quantity, which from Table 11 by inter- 
polation corresponds to 84.2°. 

27. Theoretical Amount of Moisture to be Added to Air 
to Maintain a Certain Humidity: — Warm air has a much 
greater capacity for holding moisture than cold air. When 
air of a g^iven outside temperature is heated for interior 
service, the volume increases with the absolute temperature 
(See Art. 15). On the other hand, the relative humidity de- 
creases rapidly as shown by the humidity curves (Fig. 9). 
Air that is dry is unpleasant to the occupants, as well as 
being detrimental to the furnishings of the room. Therefore, 
some means should be provided to supply moisture to the 
incoming air current. In calculating- the amount to be 



52 



HEATING AND VENTILATION 



added, let Q = cubic feet of air per hour entering the room 
at the register temperature t, Q' =z corresponding- volume at 
room temperature t' and humidity u-, Qo = corresponding 
volume at outside temperature to and humidity Uo. Also let 
T, T' and To be the absolute temperatures of the entering air, 
room air and outside air respectively. From the equations 
TQ' — T'Q and TQo = ToQ (17) 

find Q' and Qo. From Tables 11 or 13, Appendix, find the 
amounts of moisture M' and Mo in one cubic foot of saturated 
air at the temperatures t' and to, multiply these by the re- 
spective humidities and volumes, and the difference between 
the two final quantities will be the amount of moisture re- 
quired per hour as expressed by the equation 

W = Q'M'u' — QoMoUo (18) 

Application. — Let Q = 5000, t = 130, f = 70, to = 30, 
u' = .50, Wo = .50, M' =. 7.98 and Mo = 1.935, then 
Q' = 5000 X 530 H- 590 = 4490 
Qo = 5000 X 490 ^ 590 = 4154 
W = 13896 grains, or 1.983 lbs. per hr. 

This means that approximately 2 pounds of water would be 
evaporated for every 5000 cubic feet of fresh air entering 
the room under the above conditions (See 
also application in Art. 72). 

28. Velocity in the Convection of Air by 
tlie Application of Heat; — Let ho (Fig. 10) be 
the height of the chimney or stack. If the 
temperature of the gases within the chimney 
CD be the same as that of the entering air 
there will be no natural circulation, because 
the column CD will just balance a corre- 
sponding column AB upon the outside. If the 
teniperatures of the chimney gases CD and 
entering air be tc and to respectively, the 
chimney gases being (tc — to) degrees above 
that of the outside air, then upon entering the 
chimney the air becomes less dense and ex- 
pands according to the ratio of the absolute 

B' — iQ temperatures before and after heating. With 

Fig. 10. an outside column of ho feet, it Avill require 

a column of the chimney gases ho + he feet to produce 
equilibrium. In other words, the equivalent column of gases 



MEASUREMENT OF AIR VELOCITY 53 

producing circulation in the chimney has a height of Jic feet. 
Assume, in the system ABCDE, that the interior cross sec- 
tions at all points are uniform. The volumes of AB (imag- 
inary column) and CE (actual column) are to each other as 
their respective heights, and 

Vo : Vo + Vc :: Jio : ho + he, or Jio : 460 + to :: ho + he : 
460 + tc. From this we obtain he (460 + to) = ho (tc — to) 
and 

ho (te — to) 

he = (19) 

460 + to 

Substituting for h in the equation v = \/2 gh, its correspond- 
ing value he, we have 



Vhu {tc — to) 
460 + to 



V2 ghe = 8. 02-. • (20) 



It is found in practice that the theoretical velocity as 
given by this equation is never obtained because of the loss 
of draft due to the friction between the column of gases and 
the sides of the chimney, and from wind pressures and 
other causes. Some engineers estimate the actual discharge 
from the chimney at 50 per cent, of the theoretical. This 
estimate may be fairly safe for medium sized chimneys but 
will not be realized on the smaller ones used in residences, 
which will probably be 25 to 50 per cent, of the theoretical. 
As the transverse net area becomes smaller, the percentage 
of friction to the total air moved increases very rapidly and 
soon becomes the principal factor. Prof. Kent assumed a 
layer of gases two to three inches thick next to the interior 
surface as having no velocity and consequently ineffective. 
Thus a minimum of 4 inches would be added to each theoret- 
ical cross dimension to obtain the nominal size of a rec- 
tangular chimney. 

Some uncertainty will be experienced. in the selection of 
the best values for the average temperatures of the chimney 
gases, tc, and the outside temperature, to, for calculations. 
tc is low for residence chimneys because of the low rate of 
combustion (3 to 7 lbs. per sq. ft. of grate per hr.) and high 
for large apartment houses, office buildings and power 
plants (10 to 24 lbs. per sq. ft. of grate per hr.). It is low 
for unprotected chimneys having large heat loss from radia- 
tion and high for those that are housed-in with the build- 



54 



HEATING AND VENTILATION 



ing". Assume to = 70 for all calculations. Approximate 
values for chimney height above the grate, ho, average tem- 
perature of gases in chimney, tc, and temperature of gases 
entering chimney, tb, may be taken as in Table V. 

TABLE V. 



Residences 


Apartment houses 


ho 


30 


40 


50 


60 


tc 


200 


225 


260 


300 


tb 


300 


350 


400 j 450 



To estimate the approximate volume of gases circulating' 
through the chimney per second, multiply the pounds of coal 
burned per hour by 25 (pounds of g-ases per pound of coal, 
maximum) times the specific volume of the g"as at the tem- 
perature of the entering chimney gases and divide the result by 
3600. Note that the average temperature of the gases is 
used in obtaining- draft but that the entering temperature is 
used in obtaining- area, since all transverse areas are equal 
and calculated to carry the gases at the entering- volume. 

When Equation 20 is applied to hot air stacks in heating sys- 
tems, allowances for friction are much less because of the 
smooth interior of the duct. In such cases the actual veloc- 
ity of the air should approach more nearly the theoretical. 
(For applications to chimneys see Arts. 31 and 32). 

29. Measurement of Air Velocities: — (See also Arts. 144- 
146), In ventilating -work it is often of the greatest im- 
portance to determine air velocities accurately. The correct 
selection of the sizes of air propelling fans or blowers to do 
a given work depends largely upon the 
measurement of the velocity of air de- 
livery. In acceptance and other tests 
this measurement is equally important. 
Velocities are most commonly meas- 
ured by means of a vane wheel instru- 
ment called the anemometer. It is essen- 
tially a delicately pivoted wheel having 
from six to fifteen vanes and similar to 
the common wind mill wheel (See Fig. 
11). To the shaft is connected a re- 
cording mechanisni consisting of a set 
Fig. 11. of dials which show the velocity of the 




MEASUREMENT OF AIR VELOCITY 



55 



air traveling past the instrument. By reading this recording 
mechanism against a stop watch the velocity of the air per 
unit of time may be obtained. Since the instrument works 
against the friction of moving parts its readings are sub- 
ject to variation and even with frequent calibrations it is 
not wholly to be relied upon. Various tests of anemometers 
in comparison with the absolute readings of a gas tank 
have shown errors as high as 35 per cent, slow to 14 per cent, 
fast, in the discharge from pipes 8 inches to 24 inches in 
diameter. It is not fair to condemn a type of instrument 
because some instruments of the class have failed through 
long service or lack of care, but in general it is safe to say 
that the anemometer as an instrument for delicate velocity 
measurement should be used with great care and should be 
frequently calibrated. 

Velocities are also measured by the Pitot tube, Fig. 12. 
This method of measurement is not as simple as the ane- 
mometer but when properly applied it is more accurate. The 
Pitot tube is essentially a pressure measurer. In every mov- 
ing fluid (liquid or gas) three pressures are acting. These 
are commonly designated dynamic, static and velocity. Let the 



iji i 




^//////////AV/.'///^/ 



Fig. 12. 



bent tube A be partially filled with mercury, oil or water as 
shown and let it be inserted in the pipe with the open end 
square against the stream. Also, let tube B be similarly 
constructed but let the plane of the opening be 90 degrees 
to A. Tube A is acted upon inside the pipe by the atmos- 
phere plus the total forward pressure of the stream (dy- 
namic pressure) and on the outside by the atmosphere. 
Tube B is acted upon inside the pipe by the atmosphere plus 
the cross pressure (static pressure) and on the outside by 
the atmosphere. In each case the liquid in the bent tube 
ghows unequal levels, A having greater depression than B, 



56 HEATING AND VENTILATION 

Now if the two tubes are united as in C so that the pipe 
pressures act on opposite sides of the same liquid column, 
the atmospheric pressure is eliminated and the two internal 
pressures subtract, giving- velocity pressure, i. e., 

dynmnic pressure — static pressure = velocity pressure, 

G shows the instrument as commonly applied. In this the 
subtraction is automatic and the difference in levels, hw, is 
caused by the velocity pressure only. To find the actual 
velocity of the air in the pipe apply the equation v = V2 gh 
where ii = velocity in feet per second, g = acceleration of 
gravity in feet per second, per second and h = the velocity 
head of the air in feet. If the tube contains water at 60°, 
the ratio between the specific gravities of air and water be- 

62.37 

ing = 816.4 (See Tables 9 and 13, Appendix), the equa- 

.0764 

tion reduces to 



V = \/2 X 32.16 X 816.4 X htv -^ 12 or 

V = 66.2 Vh~ (21) 

where hw = the difference in height in inches of the water 
columns with both legs connected as described and at a tem- 
perature of 60°. By a similar method this equation may be 
deduced for a mercury or other liquid column, or for other 
temperatures than 60°. 

Several Pitot tubes, differing from each other slightly in 
features of design, are in commercial use. Because of these 
mechanical differences their readings do not absolutely 
check each other or those from the theoretical formula, 
hence all readings must be multiplied by a constant charac- 
teristic of the tube in use (See Trans. A. S. H. & V. E., Vol. 
XXI, p. 459). 

In using the Pitot tube or the anemometer, the fact 
should not be lost sight of that the velocity varies from a 
minimum at the inner surface of the pipe to a maximum at 
the center. The friction on the inner surface causes the 
moving fluid to be retarded next the pipe wall and any test, 
for velocity must account for this variation. With a circular 
pipe the change of velocity may be approximately repre- 



MEASUREMENT OF AIR VELOCITY 



57 



sented by the abscissae of a parabola %vith its axis on the 
axis of the circular pipe (See Fig. 13). 

The point of average velocity is variously quoted from 
one-fourth to one-third the radius from the wall toward the 
center, the value depending probably upon the character of 
the inner surface of the tube. For general use three-tenths 
will give good average values. For conduits of other shapes 
the position of mean velocity is difficult to determine. The 
only safe way is to divide the cross section into small areas 
and take readings in each area to obtain the average. This 




Fig. 13. 

variation of velocity from the center of the stream lessening 
toward the walls may possibly account for many of the 
variations shown by anemometer tests. It is evident that 
it is difficult to locate an anemometer so that it will give 
the correct average reading. In large ducts the error will 
be less. Pitot tube measurements are more easily applied 
and are more reliable. 

Automatic recording meters may be obtained for keep- 
ing permanent records of the flow of air and steam through 
ducts and pipes. The record from the meter indicates di- 
rectly the cubic feet of free air or other fluid circulating 
during each hour of the day. 

References. — Kent, Mechanical Engineers Pocket-Book. Trans. 
A. S. H. & Y. E. Report of the Committee on the Best Way 
to Take Anemometer Readings, Vol. XIX, p. 202. On Stand- 
ardization of Use of Pitot Tube, Vol. XX, p. 210. Measure- 
ment of Air Flow, Vol. XXI, p. 450. Trans. A. S. M. E. Meas- 
urement of Air in Fan Work, Vol. XXXIV, p. 1019. The 
Pitot Tube, Vol. XXV, p. 184. Jour. A. S. M. E. Pitot Tubes 
for Gas Measurement, Sept. 1913, p. 1321. 

30. To Determine the Transverse Area of a Chimney 
for Any Given Height: — The value of any flue as a carrier 



58 HEATING AND VENTILATION 

of heated gases depends upon both velocity and transverse 
area. It is not only necessary that a chimney have suffi- 
cient height to produce draft but it must have an area 
capable of carrying- the total volume of the gases. The 
height may be sufficient to create a good velocity but the 
area may not be sufficient to carry the volume of gases 
required and the draft becomes ineffective because of clog- 
ging. On the other hand, the draft may become ineffective 
from reduced velocity due to too large an area. In any 
chimney, height and area are dependent variables. The 
height is first determined to give a certain draft and to 
agree with surrounding building conditions, after which 
the area is determined to carry the gases at the given 
chimney height and resulting gas velocity. To obtain the 
theoretical size of a chimney, substitute Jio and the assumed 
values of tc and to in Equation 20 and determine the velocity 
of the gases per second. Divide the estimated maximum 
volume of gases moved per second by the velocity to de- 
termine the transverse area in square feet and reduce this 
value to a corresponding round, square or rectangle. For 
the actual size add a minimum of 4 inches to each theoretical 
dimension. 

31. Small Chimneys: — Application for a ten room residence. 
Given: total heat loss from the building per hour 100000 B. t, 
u., coal 13500 B. t. u. per pound, furnace efficiency 60 per cent, 
temperature of chimney gases at base of chimney 300°, 
average temperature of chimney gases 200°, outside tem- 
perature 70° and height of chimney 30 feet above the grate. 

A heat loss of 100000 B. t. u. per hour will require 
100000 -H (13500 X .60) = 12.35 pounds of coal per hour at 
the grate. With gases 300° temperature there will be moved 
12.35 X 25 X 19.14 = 5933.4 cubic feet of gases per hour. 
The velocity of the chimney gases according to equation is 
21.8 feet per second, which gives 144 X 5933.4 -=- (3600 X 
21.8) = 10 square inches, or 3.2-in. X 3.2-in. Adding 4 inches 
to each dimension = 7.2-in. X 7.2-in., say 8.5-in. X 8.5-in. 
to fit the brick work. If this were an outside wall chimney 
it should be 8.5-in. X 13-in. 

Application for an apartment house or small school. Given: 
total heat loss from the building per hour 1000000 B. t. u., 
ho = 60, tc = 300, tb = 450, to = 70, and the coal and air con- 
ditions as above, find the sizes of the chimney, 8.5-in. X 8.5- 



CHIMNEYS 59 

in. (theoretical) and 13-in. X 13-in. (actual). For an out- 
side chimney, at least 13-in. X 17.5-in. 

In small chimney construction there is a tendency to 
leave the interior of the brick work very rough. This should 
not be, but where such methods are allowed, one dimension 
of the actual sizes determined as above should be increased 
by the width of one brick. 

33. Large Chimneys: — Chimneys for office buildings, 
power plants, etc., are generally rated in terms of boiler 
horse-power. To calculate the sizes of such chimneys, first 
find the intensity of draft (pressure of the current of gases 
in inches of water, determined by a draft gage). This will 
vary from .75 in. to 1.25 in., according to the type of boiler, 
method of firing, and length and size of breeching. See 
books on power plant operation. Having the draft, find 
the height of the chimney, Jio, by the equation 



.52 7(c 



Po\ ) (22) 



where d = draft in inches of water, po = observed atmos- 
pheric pressure (commonly taken 14.7), To = absolute tem- 
perature of outside air and Ti = absolute temperature of 
gases in chimney. Having lio, find the diameter of a round 
chimney by the equation 

B. H. P. = 2.4 D^y/hT (23) 

where B. H. P. = nominal boiler horse-power and D r= 
diameter of chimney in feet. For square chimneys find the 
equivalent area of the round chimney. 

Application. — Find the height and diameter of a chim- 
ney for 1000 boiler horse-power. Temperature of gases 
500°, outside air 70° and required draft, 1-inch of water. 
In Equation 22 



1 = .52 X 14.7 7(« I I 

\ 530 960 / 



ho = 150 ft. 
Also substituting in Equation 23 

1000 = 2.4 Z)2 VlTo 

D = 5.8 ft., say 6 ft. 
33. Chimney Notes: — The ideal chimney flue is round in 
section. Most building construction, however, requires rec- 
tangular shapes. These should be kept as nearly square as 
possible. No chimney fiue should be built less than 8-in. X 



60 HEATING AND VENTILATION 

8-in. All chimneys should be built up of liarcl burnecl bricks 
well bedded in cement mortar. All joints should be struck 
smooth. Interiors are improved if lined with hard burned fine 
tiles. Chimneys should be built free from other house con- 
struction so as to permit the unequal expansion and con- 
traction without cracking- the walls of the house or the 
chimney. The top of the chimney should extend above the 
highest point of the building. If the top is below any near- 
by portion of the building, eddy currents will be formed 
which will enter the top of the flue and seriously reduce 
the draft. Under such conditions a shifting cowl may be ad- 
visable. Chimneys under 30 feet in height are unreliable in 
their action. Some engineers recommend nothing under 40 
feet. The chimney should have no other openings into it 
than the furiiace or boiler smoke pipe. Chimneys in outside 
walls are not as satisfactory as when built-in, due to the 
chilling effect of the outside air. When an outside wall chim- 
ney is put in it should be made double walled with air space 
between the walls. A warm air flue by the side of a chim- 
ney is an ideal location for the flue. All chimneys should 
rest upon solid foundations. All joints between the boiler 
and the chimney should be tight to preserve the draft. Good 
draft is very essential to the success of any type of heating 
system, and the purchaser should be required to guarantee 
a sufficient draft and capacity of his chimney before the 
manufacturer should be expected to guarantee a stated rat- 
ing of his furnace, heater or boiler. 

References. — Christie, Chimney Design, Gebhardt, Steam 
Power Plant Engineering, Marks, Mechanical Engineers Handbook, 
Kent, Mechanical Engineers Pocket-Book, H. & Y . Mag. Baldwin 
on Chimneys, Oct. 1913, p. 23, Jan. 1914, p. 31. 

34. Cowls and Ventilator Heads: — The capacity of any 
vent or chimney flue may be increased by properly designed 
cowls surmounting the top of the opening. Much of the 
down draft experienced under changing wind pressures may 
thus be eliminated. Shifting heads or cowls take advantage 
of any wind velocity to increase the upward movement of 
the air by induction and, when fitted with bearings that per- 
mit adjustment from the slightest wind velocity, may be 
considered highly desirable. 



CHAPTER III. 



HEAT LOSSES FROM BUILDINGS 



35. Heat Dissipsited from Buildiug-s : — In planning- the 
heating system for any building-, the first and most impor- 
tant part of the work is to estimate the total heat lost in 
B. t. u. per hour from building. Unfortunately this is the 
part which is open to the least satisfactory calculation be- 
cause of varying wind conditions and imperfections in build- 
ing construction, and because of the lack of accurate con- 
ductivity values, especially those relating to the more recent 
building materials. 

Heat is lost from a building in three ways: first, that 
transferred through the walls, windows and other exposed 
building materials by conduction and lost by radiation and 
convection; second, that carried away by convection air cur- 
rents that pass out through wall cracks and door and win- 
dow openings to the outside air; third, that lost through 
specially prepared ventilating ducts. The third item is not 
included in the usual building heat loss (See Arts. 41 and 42). 
In the average building the conduction loss is the principal 
one, although it is now found that the convection loss is of 
much more importance than has been generally considered. 
In Siny case neither of these losses can be determined ex- 
actly, but close estimations may be made. 

36. Conduction and Radiation Losses: — These losses are 
considered under various heads, such as glass, wall, floor, 
ceiling and door losses. AA'ailable data have been obtained 
by experimentation but these do not agree very closely. The 
reason for so much uncertainty in this part of the heating 
work is found in the fact that there are great differences in 
methods of building- construction. Conductivity tests on 
simple materials give fairly uniform results, but when these 
same materials are assembled in building walls the quality 
of the workmanship often permits more heat loss by con- 
vection than would be transmitted through the materials 
by conduction. The values quoted for glass and the more 
compactly built up structures such as brick walls, agree 
fairly well. The greatest difficulty is found in the balloon 
frame building with its studded walls, where the dead air 
space in a well constructed wall may be a good noncon- 



62 



HEATING AND VENTILATION 



ductor, or where on the other hand the same space in a 
poorly constructed wall may become a circulating air space 
to cool the walls by the movement of the air. 

As an illustration of what may be expected in building 
losses let Fig. 14 represent a 4-inch studded wall with a 
tight air space between the studding. It is built up of ma- 
terials each having a different conductivity and is sub- 
jected upon one side to the room temperature %' and upon the 
other to the outside temperature to. Let aa', 66', cc', etc., be 

planes of equal temperature', but 
each plane having less inten- 
sity of temperature, in the order 
named, betv/een t' and to. Also 
let the curve xyx represent the 
temperature drop (measured on 
the ordinates above an arbi- 
trary zero, not marked) in the 
heat travel between the enter- 
ing and leaving radiant heat 
rays, x and s. It will be noticed 
that the temperature drop is not 
uniform along the path of heat 
travel. This is because of the 
varying conductivities of the 

different materials passed 

through. Along every heat path 
■^^S"- ^^- there are three resistances to 

the flow of heat between t' and to; the air envelope 
In contact with the wall, the materials composing the 
wall and the surfaces of each material composing the 
wall. The summation of these resistances represents 
the insulating effect against heat flow. It is desir- 
able that these resisting surfaces and materials be of 
such a character as to cut off heat flow across the wall as 
completely as possible. The common defect found with such 
wall combinations is loose construction and air circulation be- 
tween the studding. Since the insulating effect of any ma- 
terial or combination of materials is proportional to the 
total resistance along the heat path, free air circulating be- 
tween the studding, say from basement to attic, would cause 
an increased heat loss because the resistances through the 
latter half of the wall would be eliminated. If, in Fig. 14, 




HEAT LOSSES FROM BUILDINGS 63 

the air space marked stud were not tightly closed at bottom 
and top, the heat crossing from ce' to dd' would be carried 
away by convection and the insulating qualities of the wall 
would be R' as compared with /? in a tight wall. Still air 
is a good nonconductor. Convected air is a good heat car- 
rier. Walls of other construction give less uncertainty in 
heat calculation. 

Theoretical equations for heat losses through building 
walls are based upon conductivity values (reciprocals of re- 
sistances per unit thickness) of the various materials and 
do not take into account such incidental points as interven- 
ing air spaces and poor construction. Since the amount of 
heat transmitted is equal to the temperature drop divided by the sum 
of the resistances, we have for any combination of materials 
(assuming all surfaces in contact and no air spaces), Hu = 

(r — to) -^ (Ra + Rb + Re + + Ki + i?2 + iJa + ), 

where Ra, Rb, Ro, etc., are the resistances of the materials 
and i?i, i?2, i?3, etc., are the surface resistances per unit area. 
With the material thicknesses m, n, o, etc., and the conduc- 
tivities Ka, Kb, Kc, Ki, K-y, Kz respectively. 

r — to 

Hu = (24) 

m n 111 

+ + + + + + , etc. 

Ka Kb Kc Ki K2 Ks 

Collecting the conductivities in the denominator and placing 
the reciprocal of this summation as the combined conductivity 
(rate of transmission per unit area), K, we have for any 
area, A, 

H = K A (f — to) (25) 

Equation 24 is developed to illustrate a general prin- 
ciple. Its application, however, is usually unsatisfactory 
and the laborious process is unnecessary when calculating 
the heat loss for buildings, and Equation 25 is used instead. 
Values of K commonly used are obtained by experimentation. 
Table VI has been compiled from a number of the best refer- 
ences. 

TABLE VI — Value of K 

Materials K 

Brick wall, S^^" plain 37 

Brick wall, 13" plain 29 

Brick wall, 171/2" plain 24 

Brick wall, 22" plain 21 



64 HEATING AND VENTILATION 

Brick wall, 27" plain 19 

Brick wall, furred and plastered, use .7 times non-furred. 
Stone wall, use 1.5 times brick wall. 

Concrete, 2" solid 78 

Concrete, 3" solid 71 

Concrete, 4" solid 66 

Concrete, 6" solid 56 

Frame wall (plaster, lath, stud, clapboard) 50 

Frame wall (plaster, lath, stud, sheating-, clapboard) 28 

Frame wall (plaster, lath, stud, sheating-, paper, clap- 
board) 23 

Windows, single glass, full sash area 1.00 

Plate glass, same as single window glass. 

Windows, double glass, full sash area 50 

Skylight, single glass, full sash area 1.10 

Skylight, double glass, full sash area 60 

Wooden door, 1" 40 

Wooden door, 2" 36 

Hollow tile, 2", %" plaster, both sides 41 

Hollow tile, 4", %" plaster, both sides 33 

Hollow tile, 6", V2" plaster, both sides 28 

Solid plaster partition, 2" ; 60 

Solid plaster partition, 3" 50 

Concrete floor on brick arch 20 

Fireproof construction as flooring .10 

Fireproof construction as ceiling 14 

Single wood floor oh brick arch 15 

Double wood floor, plaster beneath 15 

Wooden beams planked over, as flooring 17 

Wooden beams planked over, as ceiling 35 

Lath and plaster ceiling, no floor above 62 

Lath and plaster ceiling, floor above 25 

Steel ceiling-, with floor above 35 

Single %" floor, no plaster beneath 45 

Single %" floor, plaster beneath 26 

Application. — ^With zero outside temperature the heat 
losses through the exposed glass and wall surfaces of the 
Dining Room (Pig. 18), assuming good frame construction, 
are: glass = 1 X 32 X 70 = 2240 B. t. u.; wall (minus 
glass) = .23 X 114 X 70 = 1835 B. t. u., total 4075 B. t. u. 
With — 10° outside temperature these values are 2560 -)- 
2097 = 4657 B. t. u. 



HEAT LOSSES FROM BUILDINGS 



65 



Most of the values in Table VI have been reduced to 
chart form (Fig. 15) where the resulting- values are the total 
B. t. u. transmitted through 1 square foot of the surface per 
hour. 



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Fig-. 15. 
Application 1. — Assume the outside temperature — 10°, 
i^till air, inside temperature 70° and south exposure. What 
is the heat loss from a square foot of 13-inch brick wall; 



66 HEATING AND VENTILATION 

also, from a square foot of single glass window? Beginning 
at the right of the chart at — 10° outside temperature, trace 
to the left to the wind velocity, then up the ordinate to the 
13-inch wall, then to the left to the line indicating 70° in- 
side temperature, then down to the south exposure, then to 
the left showing 24 B. t. u. transmitted per square foot per 
hour. For the glass, trace from — 10° to the wind velocity, 
then up to the single window, then to the left to the inside 
temperature, 70°, then down to south exposure, then to the 
left showing 80 B. t. u. per square foot per hour. Checking 
this with the table for a 13-inch brick wall we have, .29 X 
80 = 23.2 B. t. u. For glass, 1 X 80 = 80. The effect of the 
wind upon the heat loss is very marked. Locations subjected 
to high winds should have extra allowances. For example, 
take the 13-inch brick wall just mentioned. Assume the 
wind to be 30 miles an hour. By the same process as before 
we find for a south exposure, 33 B. t. u. loss as compared 
with 24 at zero wind velocity. 

Application 2. — Assume the outside temperature — 10°, 
wind velocity 12 iniles per hour, inside temperature 70° and 
north exposure. What is the heat loss from a square foot 
of 13-inch brick wall; also, from a square foot of single 
glass w^indow? Trace as before and find 31 B. t. u. for the 
wall and 105 B. t. u. for the glass. This is an increase of 
approximately 30 per cent, over Application 1, due to ex- 
posure and wind velocity. 

Application 3. — Assume the attic temperature 20°, zero 
wind velocity, south exposure, room temperature 70", lath 
and plaster ceiling with no floor above. "What is the heat 
loss through a square foot of ceiling per hour? Trace from 
20° outside temperature and find 32 B. t. u. Checking this 
with the table, .62 X 50 = 31 B. t. u. 

Application 4. — Work out Application 3 for a steel ceiling 
with floor above and check with the table value. 

Application 5. — Assume a 4-inch concrete floor laid on 
the ground, with a ground temperature of 40° and an air 
temperature at the floor line of 65°. What is the heat loss 
through a square foot of the floor per hour? Trace from 
40° outside temperature to zero wind velocity, down to 
4-inch solid concrete, to the left to 65° temperature, down 



HEAT LOSSES FROM BUILDINGS 67 

to south exposure and to the left to 17 B. t. u. Check by 
Table VL 

Application 6. — Assume a 6-inch concrete floor on ground 
with a ground temperature of 50° and an air temperature at 
the floor line of 65°. What is the loss through a square foot 
of the floor per hour? Trace from 50° outside temperature to 
zero wind velocity (extended), down to 6-inch solid concrete 
(extended), to the left to 65° temperature, down to south 
exposure and to the left to 9 B. t. u. Check by Table VI. 

37. lioss of Heat by Air Leakajpe: — Buildings are sub- 
ject to air leakag-e throug'h walls, floors, ceiling's and win- 
dow and door clearances. No effort is made to estimate the 
leakag-e throug'h walls. In the best type of windows, metal 
weather strips or other insulations are used. Most of the 
estimates of building- heat losses, however, have to do with 
ordinary window construction, the quality of the workman- 
ship of which is frequently very poor. Experiments made 
by H. W. Whitten, R. C. March, S. F. Voohees and H. C. 
Meyer (Trans. A. S. H. & Y. E., Vols. 15 and 22; also, Jour. 
A. 8. H. & V. E., Jan. 1916) to determine the amount of leak- 
age around windows and doors, were very successful in the 
specific cases. The application of the conclusions to g-eneral 
rules, however, is open to much g'uess work, since a well 
fitted window has approximately ^^g-inch clearance, while a 
loosely fitted window may have as much as ^^^-inch. In the 
tests it was shown also that in any g-iven window clearance 
the leakag'e varied greatly as the outside air velocity varied. 
For illustration, with a clearance of iV-inch the leakag'e in- 
creased 25 per cent, per mile increase of wind velocity; or for 
a four mile increase in wind velocity the leakag'e loss in- 
creased 100 per cent. With such variations as this the heat 
loss allowance for the averag'e window leakag'e is a question. 
Reg-ardless of the uncertainty in this part of the work, it is 
interesting- to make the best approximation possible and use 
this in estimating' the heat loss from the building'. 

Some of the approximate values determined by the tests 
were: 

(1) Averag'e wind velocity in localities where 

heating- is important, miles per hr 13 

(2) Averag'e sash clearance, in -^ 



68 HEATING AND VENTILATION 

(3) Air pressure equal to a 15-mile wind against 

a window having ig-in. clearance will force ■ 
146 to 185 cu. ft. of air throug-h each lineal 
ft. of window clearance per hr. R. P. Bol- 
ton recommends 90 cu. ft. Harding and 
Willard use 60 cu. ft. 

(4) Metal weather strips, etc., reduce the leakage 

as low as 1-5 to 1-9 of that found in the 
average wood frame window. 

(5) The lineal perimeter of the average window 

is numerically approximately equal to the 
window area in sq. ft., = G. 

From these an estimate may be made for cubic leakage 
losses through the average window per hour. 

Application 1. — What is the window leakage loss from 
the Living Room, Fig. 18? With a window perimeter = G, 
a 15 mile wind and a iV-in. clearance we have (assuming 
100 cu. ft. per hr. per lineal ft. of perimeter), 42 X 100 = 
4200 cu. ft. of air per hr. Since the room is 13' x 15' x 10' = 
1950 cu. ft. this leakage would amount to 4200 -h 1950 = 2.15 
room volumes per hr. 

Application 2. — What is the leakage loss from 

(a) Dining room? = 3200cu.ft.hr. = 1.52 room volumes 

(b) Study? — 4800 cu. ft. hr. = 2.53 room volumes 

(c) Kitchen? G only = 3200 cu. ft. hr. = 2.32 room volumes 

(d) Kitchen? G -h door = 5000 cu. ft. hr. — 3.62 room volumes 
Professor Carpenter in his heat loss equation makes al- 
lowance for leakage losses by using the factors n G for 
leakage air, in the term .02 n C, where n = number of room 
volumes and C = volume of the room in cubic feet. The 
use of the term .02 n C is very common practice among heat- 
ing engineers. The constant .02 is determined as follows: 
The specific heat of air at 32° is .238; then the number of 
pounds of air heated from 32° to 33° by 1 B. t. u. is 1 -^ .238 = 
4.2. If the weight of a cubic foot of air at 32° is .0807 
pounds, we have 4.2 ^ .0807 = 52 cubic feet of air heated by 
1 B. t. u. Since most of the heating is done at an average 
temperature of 70° the volume of air heated from 69° to 70° 
by 1 B. t. u. is 52 X 530 -f- 492 = 56 cubic feet (See absolute 
temperature, Art. 4). It is evident that some approximation 
must here be made. No exact value can be taken because 



HEAT LOSSES FROM BUILDINGS 69 

of the great range of temperature change of the air, but 55 
is probably the best average. The difficulty of handling the 

1 

equation with the constant has led to the simple form .02. 

55 
(See last column Table 13, Appendix). 

38. Exposure and Other Allowances: — Air at high veloc- 
ity passing over the surface of any radiating material is 
more effective in removing heat than air at low velocity. 
The north, northwest and northeast in most sections of the 
country are subject to the highest winds and have the least 
benefit from the sun, and are therefore counted the cold por- 
tions of the building. In estimating heat loss a good 
way is to figure each room as if it were a south room (as- 
sumed to need no additions for exposure) and add a certain 
percentage of this loss for exposure to fit the real location 
of the room. The exact amount to add in each case is 
largely a matter of the judgment of the designer, who of 
course is supposed to know the direction of the heavy winds 
and the protection that is afforded by surrounding buildings. 
Values covering American practice vary between the limits 
given in Table VII. * 

TABLE VII. — Exposure. 

North, northeast and northwest rooms heav- 
ily exposed 10-25 per cent. 

East or west rooms moderately exposed -.. 5-15 per cent. 

Rooms heated only periodically 20-40 per cent. 

Heat interrupted daily but rooms kept closed.. 10 per cent. 

Heat interrupted daily but rooms kept open.... 25 per cent. 

Heat off for long periods 50 per cent. 

Rooms 12 to 141/^ feet from floor to ceiling 3 per cent. 

Rooms 141/^ to 18 feet from floor to ceiling 6 per cent. 

Rooms 18 feet and above from floor to ceiling" 10 per cent. 

39. Calculation of the Heat Losses — Rule: — Estimate for 
all rooms to be heated, the number of square feet respec- 
tively of exposed glass surface (full sash area), exposed wall 
surface (gross wall minus glass), exposed doors, floors above 
unheated or partially heated spaces, ceiling's immediately be- 
low attic spaces, and partition walls between heated and un- 
heated spaces. With these values and by the use of Table 
VI, multiply each surface area by its respective value of K and l)y 
the temperature difference between the two air envelopes on the 



70 HEATING AND VENTILATION 

sides. To the sum of these products add the amount .02 times the 
cubic feet of air change per hour times the temperature difference 
between the inside and outside air, and this will represent the heat 
loss for a southern exposure. For other exposttres add amount 
allowed for losses due to location f'rom Table VII. 

Application 1. — Referring to Fig. 18, the Living Room 
will have a heat loss on a zero day as follows: glass, 
1x42x70 = 2940 B. t. u. ; wall, .23x263x70 = 4234.30 B. t. 
u.; floor (assuming 40° in this part of basement), 45 x 195 x 
30 = 2632.50 B. t. u.; and air change (See Table VIII), 
.02x2x1950x70 = 5460 B. t. u. Total 15267 B. t. u. Since 
this is a south room there is no allowance for exposure. 

The above rule may be stated in equation form. Let 
ff = B. t. u. heat loss from room per hour. "With areas in 
square feet, let G = exposed glass, W = exposed wall minus 
glass, D = exposed doors, F = floor or ceiling separating 
w^arm room from unheated space, etc. Also let tx = 
(f — to) = difference between room temperature and outside 
temperature; ty = (f — t") = difference between room tem- 
perature and temperature of the unheated space; K, K' and 
K" = ''coefficients of heat transmission; Q = nC in Arts. 37 
and 40 = cubic feet of air change per hour, and a =r per- 
centage allowed for exposure. Then 

E = {KOtx + K' Wtx + K" Fty + Etc. + .02 Q/.) (1 + a) (26) 

Application 2. — With same data as in previous application 
H = (1x42x70 + .23x263x70 + .45x195x30 + 
.02x2x1950x70) (1 + 0) = 15267 B. t. u. 

Good judgment is necessary in selecting the proper out- 
side temperature, to, for any locality (See Art. 63). Room 
temperatures for heated rooms, f, may be taken from Table 
IX, and temperatures for unheated rooms and spaces from 
Table X. 

Certain credits tending to reduce H are frequently made 
to the heat loss calculation by allowing for the heat dissi- 
pated from lights, persons, etc., within the room (See Art. 44). 

40. Short Rules for Estimating Heat Loss: — The method 
of estimating heat losses outlined in Art. 39 can be recom- 
mended for any heat loss calculations. Engineers of experi- 
ence, however, occasionally develop modifled forms for their 
own use, based upon the method shown in Art. 39 and suited 
to average building conditions. These short cut methods 



HEAT LOSSES FROM BUILDINGS 71 

should be used with caution by persons not thoroughly 
acquainted with their development. 

Carpenters' Rule. — According- to Prof. R. C. Cerpenter 
the quality of building- construction and the corresponding 
heat losses from these buildings are so varied and uncertain 
that elaborate methods of figuring heat losses are unneces- 
sary. He recommends K = .25 for any ordinary wall sur- 
face and (t — 1 for any glass surface. Ceiling and floor sur- 
faces, where it is thought necessary to consider them, may 
be reduced to equivalent wall surfaces. The rule therefore 
becomes a simple modification of Equation 26, where tx = 
r — to. 

H = (G + .25W -\- .02 nC) (f — U) + exposure (27) 

TABLE VIII — ^Values of n 

Residence heating: halls and bath rooms, 3; living rooms and 
rooms on the first floor, 2; sleeping rooms and rooms on 
second floor, 1. 

Offices and stores: first floor, 
2 to 3; 
second floor, 1% to 2. 

Churches and public assembly 
rooms, % to 2. 

Large rooms with small ex- 
posure, % to 1. 



r 

The author w^ould suggest 
that frame construction, 
large window areas and 
relatively small volumes 
tend toward the larger val- 
ues of n; conversely, brick 
construction, small window 
areas and relatively large 
volumes tend toward the 
smaller values of n. 



With Equation 27, Table VIII should be used and the 
following wall equivalents may be employed with good effect: 

Doors not protected by storm doors or vestibule, with or 
without small amount of glass = 200 per cent, of equal wall 
area. 

Floors over unheated closed spaces = same as wall. 

Floors over partially heated closed spaces = 50 per cent, 
of equal wall area. 

Ceilings below unheated closed spaces, no floors above = 
200 per cent, of equal wall area. 

Ceilings below unheated closed spaces, floors above = 50 
per cent, of equal wall area. 



72 HEATING AND VENTILATION 

Application 8. — With the same room and data as in Ap- 
plication 1. 

H = 1^2 + .25 X (263 + .5x195) + .02x2x1950] 70 = 
14707 B. t. u. 

Harding and Willaed^s Rule. — This is a modification of 
Carpenter's Rule with the term .02 nC replaced by a leakage 
factor in terms of the window and door perimeter, P. Use 
window and door perimeter on that outside wall having the 
greatest amount of window and door surface. 

H = ((? + .25 W + CP) (f — to) + exposure (28) 

Where the value of G is taken for 

Good construction — 3^2 -in. sash clearance.... 1.2 

Poor construction — le-in. sash clearance 2.4 

Weather stripped sash 0.15 

Application 4. — With the same room and data as in Ap- 
plication 3, assuming both w^indows to be affected simul- 
taneously by the air pressure 

H, Good Const. = [42 + .25 (263 + .5 x 195) + 1.2 x 42] 
70 = 12747 B. t. u. 

H, Poor Const, r: [42 + .25 (263 + .5 x 195) + 2.4 x 42] 
70 = 16303 B. t. u. 

One of the difficulties in the application of Equation 28 
is to determine the character of the sash clearance. In all 
probability the average value C will approach 2.4 rather 
than 1.2. 

41. Loss of Heat by Ventilation: — Heating and Ven- 
tilating systems should have special provisions made for 
supplying fresh outdoor air for the inhabitants of the rooms 
and exhausting a corresponding amount of foul air. The 
exhausted air is usually warm air and as it leaves the rooms 
carries a certain amount of heat with it. This is a direct 
loss and should be taken into account. 

Since the loss by leakage is the same for any building 
regardless of the heating system employed, it is accounted 
for in the ordinary heat loss equation, but losses through 
ventilating systems must be considered in excess of this 
amount. Let Qv = cubic feet of fresh air supplied through 
the ventilating system per hour, f — to = drop in tempera- 
ture from the inside to the outside air; then the heat lost by 
exhausting the air is 

Qv (f — to) 

Hv = (29) 

55 



HEAT LOSSES FROM BUILDINGS 73 

42. Combined Heat Loss, H' — {H -\- Hv): — In building-s 
where ventilation is provided, the total heat loss is that lost 
by conduction and radiation, H, + that lost by ventilation, Hv 
(See also Art. 50). 

Qv if — to) 

H' = H + (30) 

55 

Rule. — To find the total heat lost from any building, add to the 

heat loss calculated l>y equation, the amount found by multiplying the 

number of cubic feet of ventilating air exhausted from the building per 

hour by one-fifty-fifth of the difference betiveen the inside and outside 

temperatures. 

43. Temperatures to be Considered: — In designing heat- 
ing- systems the following temperatures may be used: 

TABLE IX— Values of f. 

Living rooms, school rooms, offices, auditoriums, lecture 

halls and general laboratories 70 

Play rooms, gymnasiums, manual training rooms, locker 

rooms and toilet rooms 65 

Bath rooms 80 

Hospitals, sick rooms and treatment rooms 75 

Greenhouses 70-80 

Shops and manufacturing plants, hard labor 60 

Shops and manufacturing plants, light labor 65 

Paint and finishing rooms 80 



Outside temperatures, to, should be estimated from the 
lowest temperature recorded by the weather bureau for that 
locality, during the preceding ten years. This will range 
from 10° in the southern to — 30° for the northern sections 
of the country. The most extreme low temperatures are of 
such short duration that one is not justified in designing for 
these. Usually ten degrees above the lowest recorded tem- 
perature is used (See Art. 63). 

The temperatures of rooms not specifically heated inay 
be taken: 

TABLE X — Values of to when applied to a room 

Cellars and rooms kept closed 32 

Rooms often in communication with the outside air, such 

as passages, entrance halls, vestibules, etc 23 



74 HEATING AND VENTILATION 

Attic rooms immediately beneath metal or slate roof 14 

Attic rooms immediately beneath tile, cement, or tar and 

gravel roof 23 

44. Heat Given Off from Lights and from Persons With- 
in the Room: — As a credit to the heating- system, some heat- 
ing engineers take account of the heat radiated from lights 
and. persons within the rooms. The following values are 
collected from various authorities and may be considered 
fair averages: 

TABLE XI. 

Gas, ordinary split burner, B. t. u. per candle power hr. 300 
Gas, Argand " " " " " 200 

Gas, Auer " " " " " 31 

Petroleum " " " " " 160 

Alcohol, incandescent " " " " " 40 

Electric, incandes'nt carbon filament " " " 14 

Electric, " metal filament " " " 4 

Electric, arc 5 

According to Pettenkofer, the mean amount of heat 
given off per person per hour is 400 heat units for adults 
and 200 for children. 

45. Performance to Guarantee Heating Capacity: — Some 
contracts guarantee that the heating system (steam or hot 
water radiation) will maintain the interior temperature of 
the building at 70° when the outside temperature is zero or 
some value below. It is frequently necessary to make tests 
to prove the fulfillment of such guarantees when the out- 
side temperature is above that stated in the guarantee. It 
Is evident that the inside temperature of the room while 
under test will the»i be in excess of 70°. To maintain the 
temperature that will give an equivalent heating value to 
the guarantee, is the object of the test. Tests of this char- 
acter are never as satisfactory as w^hen conducted under 
guaranteed conditions, but may be estimated with a fair de- 
gree of accuracy. A method proposed hy William Kent in the 
Engineering Record, Aug. 11, 1894 (See also M. E. Pocket 
Book), assumes that E is constant for any given material 
under temperature differences ordinarily found in practice; 
also, that the heat lost from the house equals the heat given 



PERFORMANCE OP HEATING GUARANTEE 75 

up by the radiator. It is found from experimental data that 
K is not constant for varying- temperature differences but 
that it may be so considered without serious error. 

Let R = sq. ft. of radiator surface; TF6 = sq. ft. of sur- 
face of exposed walls, windows, etc.; ts = temperature inside 
the radiator; t' = room temperature while under test; t = 
g-ua,ranteed room temperature; t'o = outside temperature at 
time of test; to = outside temperature specified on guaran- 
tee; Kr — rate of transmission through radiator; Ky> = aver- 
age rate of transmission through building walls. From the 
conditions of guarantee Er R (ts — t) = KbWb (t — to); c =. 
(Kt, Wb -^ Kr R); t = (ts + cto) -^ (1 + c) and c = (ts — t) ^ 
(t — to). Then from the conditions of the test 

V — (ts + ct'o) -^ (1 + c) ' (31) 

which gives the temperature of the room under test corre- 
sponding to the given values of ts and to. 

Application 1. — Suppose the heating system in any de- 
sign is guaranteed to heat the interior of the house to 70° 
at — 10° outside temperature, when the steam pressure is 
atmospheric, and that the test of acceptance is to be run 
when the outside temperature is 60°. "What will be the 
maintained inside temperature, t' , to satisfy this guarantee? 
From the conditions of the guarantee find c = (212 — 70) -r- 
[70 — ( — 10)] = 1.775. Then from the conditions of the test 
r = (212 + 1.775 X 60) ^ (1 + 1.775) =: 115°. In this same 
application if the heating system is guaranteed to heat to 
70° when the outside temperature is 0° we would have f = 
(212 + 2.029 X 60) -H (1 + 2.029) = 110°. 

A second method, very similar to the preceding and found 
in Mechanical Equipment of Buildings, Vol. 1, Harding and 
Willard also makes the assumption that K is constant for 
varying temperatures. From the two equations, (O + 
.25 W + .02 nC) (t — to) = Kr R (ts — t) and (G + .25 TF + 
.02 nO) (f — fo) = Kr R (ts — f), we have by division (f — 
Vo) -^ (t — to) = (ts — f) H- (ts — t) and 

ts (t'o + t to) t'o Xt 

r (32) 

ts to 

Application 2. — With the same conditions of guarantee 
and test as given in Application 1. t' = 115° for to = — 10° 
and 110° for to = 0. 

A third method, by W. W. Macon, is shown in Table 48, 
Appendix. 



CHAPTER IV. 



FURNACE HEATING AND VENTILATING. 



PRINCIPLES OF DESIGN. 

46. Furnace System Compared with Other Systems: — 

The plan of heating residences and other small buildings by 
furnaces in which the air serves as a heat carrier, is com- 
mon in this country. Some of the points in favor of the f ui - 
nace system are: low cost of installation, heating combined 
with ventilation, and adaptability to light service and sud- 
den changes of outdoor temperature. Compared with that 
of other heating systems, a first-class furnace system can 
be installed for one-third to one-half the cost. • In addition 
to this, the fact that ventilation is so easily obtained and 
that the consumption of fuel may be so nearly proportioned 
to the demands of the weather, give this method of heating 
many advocates. The objections to the system are: the diffi- 
culty of heating the windward side of the house, circulated 
dust, and the contamination of the air supply by the fuel 
gases leaking through the joints in the furnace. In a good 
system well installed, the only objection to be seriously con- 
sidered is the difficulty of heating that part of the house 
subjected to the pressure of the heavy wind. The natural 
draft from a warm air furnace is not very strong at best and 
any differential pressure in the various rooms will tend to 
force the air toward those rooms offering the least resist- 
ance. In a properly designed furnace plant, however, the 
layout may be so made as to reduce this possible differential 
to a minimum. The cost of operation can be largely controlled 
by the owner, consistent with his ideas of the quality of the 
ventilation needed. Arrangements may be made to carry the 
room air back to the furnace to be reheated, in which case 
(fresh air cut off entirely) the cost of heating is about the 
same as that of any system of direct radiation having no 
special provision for ventilation. Beyond this, any amount 
of fresh air desired may be taken from the outside and 
mixed with the room air for the purpose of ventilation. This 



FURNACE HEATING 



77 



requires the same amount of room air to be exhausted from 
the house at the room temperature and causes an increased 
cost of operation, as discussed in Art. 50. 

47. E]sseiitials of the Furnace System; — Fundamentally 
this installation must contain a furnace upon a proper set- 
ting, a carefully designed and constructed system of fresh 
air supply and return ducts, and the warm air distributing- 
leaders, stacks and registers. Fig. 16 shows a common 




FRESH AIR DUCT 



n?t:5H AIR DUCT 



arrangement of these essentials. Dampers in the various 
air lines in the basement provide means whereby fresh air 
may be taken from the outside or recirculated air from the 
rooms as desired. Return registers and ducts are placed in 
the coldest sections of the building (in some cases each 
room) and should lead by the shortest lines to the furnace. 
48. Points to be Calculated in a Furnace Design: — In 
addition to the calculated heat loss, H, which may be as- 
sumed the same for all methods of heating, other points in 



78 HEATING AND VENTILATION 

furnace plant design should be taken up in the following' 
order: find for each room the cubic feet of air needed as a 
heat carrier and determine if this amount of air is sufficient 
for ventilation; then obtain from this the areas of the net 
heat registers, gross heat registers, heat stacks, net vent 
registers, gross vent registers, vent stacks, leader pipes, 
fresh air duct and total grate area. From the total grate 
area select the furnace. 

49. Air Circulation in Furnace Heatings — The use of 
air in furnace heating may be considered from two stand- 
points, each very distinct in itself. First, air as a heat carrier; 
second, air as a health preserver. The first may or may not 
be fresh air. All that is necessary is to provide enough air 
to carry the required amount of heat from the furnace to 
the rooms, i. e., that amount of heat that will replace the 
heat lost by radiation plus the small amount that is carried 
away by leakage. With given temperatures of air at the 
register and in the room, the volume of air (volume at the 
register) may be easily calculated. The second requires that 
enough air be sent to the rooms to provide ventilation for 
the occupants. Each of these two amounts should be de- 
termined and the greater used in estimating the sizes of 
the registers and ducts. As previously stated^ the cubic feet 
of air per hour for ventilation may be taken 1800 N, where 
N is the number of persons to be provided for (See Art. 21). 

50. Air Circulated per Hour and Total Heat Loss: — ^A 
safe temperature t, of the circulating air as it leaves the 
heat register, is 130°. This may at times reach 150° or 
above, but it is not well to use the higher values in the de- 
sign calculations. If the room air temperature is f = 70°, 
the incoming air to the room will drop in temperature 
through 60 degrees, and since one cubic foot of air can be 
heated through 55 degrees by one B. t. u. it will give ofC 
60 -=- 55 = 1.09 (say 1.1) B. t. u. 

Let Q = cubic feet of air per hour as a heat carrier; 

H = total heat loss in B. t. u. per hour by equation; t =z 

temperature of the air at the register; and f = temperature 

of the room air; then 

55 H 
Q = ■ (33) 

t — r 

Rule. — To find the cubic feet of air necessary to carry the heat 
to the rooms, multiply the heat loss calculated hy equation l>y fifty- 



FURNACE HEATING 79 

five and divide by the difference between the register and the room 
temperatures. For ordinary furnace work this becomes 

H 

~ 1.1 

Now if this air is not specially exhausted from the build- 
ing but is taken back to the furnace and recirculated, the 
only loss of heat will be R. Since air thus used would soon 
become unfit for the occupants to breathe, it is well to ex- 
haust through ventilating- flues a part or all of the air sent 
from the furnace. This makes an additional loss of heat 
corresponding to the drop in temperature from 70° to that 
of the outside air (See Arts. 41 and 42). If the temperature 
of the outside air is assumed 0°, — 10° and — 15° respec- 
tively, the resulting heat loss will be 

H'o — H^\.11 Qv; H'-io = H+ 1.45 Q,-; H'-i5 = H + 1.54 Qv (34) 

For illustration, consider the Living Room (Fig. 18) under 
three conditions on a zero day: first, when all the air is re- 
circulated; second, when only enough air is exhausted to 
give fresh air for ventilation; third, when all the air is ex- 
hausted. Under the first case the loss H is 15267 B. t. u. per 
hour and no other loss is experienced. In the second case, 
if three people occupy the room and each is allowed 1800 
cubic feet of fresh air per hour, the total heat loss will be 
15267 + 1.27 X 5400 = 22125 B. t. u. In the third case, 
where all the air is exhausted, 15267 -^ 1.1 = 13879 cubic 
feet of fresh air per hour will be raised froin 0° to 70° 
which will increase the heat loss 1.27 X 13879 = 17626 
B. t. u., making a total loss of 32893 B. t. u. per hour. The 
second condition is that which would be found most satis- 
factory. 

It is evident from inspection that the cubic feet of air 
necessary as a heat carrier will be excessive for ventilation 
in the average residence (See Art. 51), a.nd the designer need 
not consider the amount of air for ventilation in calculating 
the sizes of the ducts and registers. However, this will be 
needed in an investigation of the size of the furnace, the 
amount of coal burned or the cost of heating; the latter be- 
ing in direct proportion to the respective total heat losses 
(See Art. 63). 

Application. — Referring to Table XII, the calculated 
amount of air Q, for the various rooms of a residence may 
be found. 



80 HEATING AND VENTILATION 

51. Is This Amount of Air Q, Sufficient for Ventilation if 
Taken from the Outside? — Assume the same room, as in Art. 
50 with Q — 13879 cubic feet. With a room volume of 1950 
cubic feet, the air will change 7.1 times per hour and, allow- 
ing 1800 cubic feet of air per person, will supply eight per- 
sons with good ventilation if fresh air is used. Stated as an 
equation this is 

n H 

N = = approx. (35) 

1.1 X 1800 2000 

As a matter of fact, ventilation for half this numbel* will be 
ample in an ordinary residence room excepting on extraor- 
dinary occasions. Test Q for other rooms and find that ducts 
and registers designed sufficiently large to carry air for heating pur- 
poses are ample for ventilation in residences. 

53. Given the Heat Loss H and the Volume of Air Q' 
for Any Room, to Find t, the Temperature of the Air Enter- 
ing- at the Registers — If for any reason Q is not sufficient 
for ventilation (schools, offices, auditoriums, etc.), more air 
must be sent to' the room and the temperature dropped cor- 
respondingly to avoid overheating the room. Let Q' = total 
volume of air per hour (including extra air for ventilation), 
measured at the register, then 

55 H 

# - 70 -j (36) 

Q' 

Rule. — When it is necessary for ventilating purposes to circulate 
more air than that calculated from the heat loss equation, then the 
temperature at the register loiU he found by ctdding to seventy de- 
grees the amount found by multiplying the heat loss by fifty-five and 
dividing by the cubic feet of circulated air. This rule applies to 
all indirect heating. 

Application. — Suppose it were necessary on a zero day 

to send 18000 cubic feet of fresh air to the above room per 

hour to accommodate ten people. The temperature of the air 

at the register should be 

55 X 15267 

i = 70 H = 116.6° 

18000 

53. Net Heat Registers: — The velocity of the air, T, as 
it leaves the heat register is assumed 3 to 4 feet per second 
by different designers. The mean value is recommended for 
registers placed near the floor line. Where they are placed 



FURNACE HEATING 81 

above the heads of the occupants of the room (See Art. 134), 
higher velocities may be used. The general equation for net 
register area in square inches is 

^ X 55 X 144 

N. H. R. = (37) 

(t — f) X V X 3600 

Rule. — To find the square inches of net heat register, multiply 
the heat loss calculated hy equation by two and two-tenths and divide 
hy the product of the velocity in feet per second times the difference 
in temperature hetioeen the register and the room air. 

Assuming a mean velocity of 3.5 feet per second for all 
floors and 60 degrees drop in temperature, from the register 
to the room, Equation 37 becomes 

fi" X 55 X 144 

N. H. R. = — = .01 H ■ (38) 

60 X 3.5 X 3600 

54. ]Vet A>nt and Return Registers: — Vent registers or 
return registers or both should be put in at every important 
part of the design, but this is not always done. In order 
that any room may be heated properly it is necessary that 
the room air be allo^ved to escape to permit the heated air 
to come in. This may be done by venting through doors, 
windows or transom.s but the ideal way is through special 
ducts to the attic or back to the furnace. A tightly closed 
room cannot be properly heated by a furnace (See Art. 67). 

If all the air were to pass out the vent or return register, 
at the same velocity as it entered through the heat register, 
the area of the vent or return register would be to the area 
of the heat register as the ratio of the absolute temperatures 
of the leaving and entering air; that is, the area of the vent 
or return register = .9 the area of the heat register. Since 
some of the air leaves the room through other openings, 
these registers need not be so large, say 



N. T. R. I 
N. R. R. j 



.007 H = .7 A'. H. R. (39) 



55. Gross Register Area: — The nominal size (catalog 
size) of the register is usually stated as the two dimensions 
of the rectangular opening into which it fits. The area of 
this opening varies from one and one-half to two times the 
net area. The larger value is for floor registers and is the 
safer one to follow unless the exact value is known for any 



82 HEATING AND VENTILATION 

special make of register. . Wall registers have lighter bars 
and for the same net area have somewhat smaller gross 
area. 

G. R. — (1.5 to 2) times the net register (40) 

Round registers rhay be had if desired. Register sizes may- 
be found in Tables 19 and 21, Appendix. 

56. Heat Stacks: — The vertical ducts delivering air to 
the registers are called stacks. To install the proper sized 
stacks in any heating system is very important. By some 
designers the cross sectional area is taken a certain ratio 
to that of the net register. This has been quoted anywhere 
from 50 to 90 per cent. Prof. Carpenter suggests 4, 5, and 6 
feet per second respectively, as the air velocities for stacks 
leading to the first, second, and third floors, Mr. J. P. Bird 
(Metal Worker, Dec. 16, 1905) used 280, 400, and 500 feet per 
minute, which is approximately 4.5, 6.5, and 8 feet per second 
for the respective floors. The cross sectional areas of the 
heat stack, with velocities 4, 5.5, and 7 feet per second, are 

fl" X 55 X 144 .0091 F 1st floor 

H. S. = = .0066 F 2nd floor (415 

60 X (4, 5.5, or 7) X 3600 .0052 H 3rd floor 

Rule. — See rule under net heat registers with changed value 
for velocity. 

The theoretical air velocity in the stack is based upon 
the equation v = V2gh, where h = (effective height of 
stack) X (^ — t') -^ (460 + *'); v is in feet per second; t is 
the temperature of the stack air; and f is the temperature 
of the room air. The calculated velocities from this equa- 
tion are much higher than those that obtain in practice be- 
cause of the retarding influence of the shape of the cross 
section, the friction of the sides, and the abrupt turns in the 
stack. 

Assuming the net register to be flgured at 3.5 feet per 
second, the quotations by Carpenter and Bird give heat 
stack areas for the first floor, 88 and 75 per cent.; second floor, 
70 and 53 per cent.; and third floor, 58 and 42 per cent, of the 
net register. Good sized stacks are always advisable (See 
Art. 71, but because of the limited space between the stud- 
ding it becomes necessary at times to put in a stack that is 
too small or to increase the thickness of the wall, a thing 
which the architect is occasionally unwilling to do. From 



FURNACE HEATING 83 

the above figures, checked by existing- plants that are work- 
ing satisfactorily., the following approximate figures will 
give good results. 

.008 H = .SN. H. R., first floor 
H. 8. = .006 H =z .6 N.H.R., second nooT (42) 

.005 H = .5N. H. R., third fioor 

57. Vent and Return Stacks: — Estimated in the same 
manner as the Isl. V. R., these may be made 

V. S. ) 

> = .1 H. 8. (43) 

R.8. j 

As a matter of practice it will be satisfactory to make these 
stacks in average residence rooms, one or more tin stacks, 
full opening between studs; the total cross sectional area 
approximating the equation. 

58. Leader Pipes: — Since all the air that passes through 
the stacks must pass through the leader pipes, it might be 
assumed that the cross sectional areas of the two would be 
equal. There are two reasons why this should not be. Be- 
cause of their vertical position, stacks offer less frictional 
resistance, area for area, than leader pipes with their small 
pitch and abrupt turns. Also there is some drop in tem- 
perature as the air passes through the leader pipes, conse- 
quently the volume entering from the furnace is greater 
than that going up the stack. Considering these points it 
would be well to make the area of the leaders 

(.008 to .009) H = (.8 to .9) N. H. R., first fioor 

L. P. = (.006 to .007) H = (.6 to .7) N. H. R., second fioor (44) 

(.005 to .006) H = (.5 to .6) N. H. R., third fioor 

the exact figures to depend upon the length and inclination 

of the leader (See Art. 69). 

59. Fresh Air Duct: — The area of the fresh air duct is 
determined largely by experience as in the case of the vent 
and return lines. It is generally taken 

F. A. D. = .8 times the total area of the leaders (45) 
Assume the average velocity of the air in the leaders to be 
6 feet per second and the area of the fresh air duct to be as 
stated, then if the air in each were of ttie same temperature, 
the velocity in the fresh air duct would be 6 -^ .8 = 7.5 feet 
per second; but since the temperatures are different, the 
velocities will be in proportion to the absolute temperatures. 
In this case — 0°, .78 X 7.5 = 5.8; at 25°, .82 X 7.5 = 6.2; and 
at 50°, .88 X 7.5 = 6.6 feet per second. It is seen by this 
that although the area of the fresh air duct is contracted to 



84 HEATING AND VENTILATION 

80 per cent, of that of the leaders, the velocity is below that 
of the leaders. It is always well to have a fresh air duct 
that is simple in cross sectional area and free from obstruc- 
tions and sharp turns. 

60. Grate Area: — The grate area of a furnace is esti- 
mated from the total heat loss, assuming the quality of the 
coal, the efficiency of the furnace, and the pounds of coal 
burned per hour per square foot of grate. The heat value 
of the coal will be between 11000 and 14000 B. t. u. per 
pound as shown in Table 15, Appendix. The efficiency of the 
average furnace is approximately 60 per cent., and the coal 
burned per square foot of grate per hour ranges from 3 to 7 
pounds (See Art. 61). Furnaces are charged from two to 
four times each twenty-four hours. ' This requires a good 
sized fire pot and a possibility of banking the fires. To 
allow 5 pounds per square foot of grate per hour is as good 
an average as can be made for most coals in furnace work. 
Let H' = total heat loss from building including ventilation 
loss, E = efficiency of furnace, f = value of coal in B. t. u. 
per pound, and p = pounds of coal burned per square foot 
of grate per hour. The equation for the square inches of 
grate area is 

H' X 144 

G. A. = (46) 

E X f X P 

Rule. — To find the square inches of grate area for any furnace, 
multiply the total heat loss from the building per hour hy one hun- 
dred and forty-four and divide by the quantity found by multiplying 
the total pounds of coal burned per hour by the heat value of the 
coal and the efficiency of the furnace. 

Application. — In the typical residence (Art. 62), H on a 
zero day is 110574 B. t. u. per hour. This will require 101000 
cubic feet of air per hour as a heat carrier. Assuming as a 
maximum that ten people will be in the house and that they 
will need 18000 cubic feet of fresh air per hour for ventila- 
tion, this air will carry away approximately 22900 B. t. u. 
per hour, making a total heat loss from the building of 
133474 B. t. u. per hour. If the furnace is 60 per cent, effi- 
cient and burns 5 pounds of 14000 B. t. u. coal per hour per 
square foot of grate, we have 

133474 X 144 

G. A. — =: 458 square inches = 24 inches 

.60 X 14000 X 5 

diameter. With coal at 13000 B. t. u. per pound, the grate 



FURNACE HEATING 85 

would be 493 square inches or 25 inches diameter; at 12000, 
534 square inches or 26 inches diameter; at 11000, 582 square 
inches or 27 inches diameter. 

In any specific case it would be wise to estimate the 
grate size from the heat value of the poorest grade of coal 
likely to be used. In this case the estimated diameter of the 
g-rate varied three inches between coal samples nominally 
rated at 14000 and 11000. This variation is too great to be 
overlooked in the selection of furnaces. With the assump- 
tion made above, the equation becomes G. A. = .0035 B' for 
the better grades of coal, and O. A. = .0044 H' for the poorer 
grades. For the average coals a fairly safe value is 

G. A. square inches = .004 H' (47) 

61. Heating Surface: — The right amount of heating sur- 
face to require in any furnace is rather an indefinite quan- 
tity. Manufacturers differ upon this point. Some standards 
may soon be expected but at present only rough approx- 
imations can be stated. One of the chief difficulties is in 
determining what is, or what is not, heating surface. Some 
quotations no doubt include surfaces that are very ineffi- 
cient. In estimating, only prime heating surface should be 
considered, i. e., plates having direct contact with the heated 
flue gases on one side and the warm air current on the 
other. If these plates transmit K, B. t. u. per square foot 
per degree difference of temperature, tz, per hour; and if one 
square foot of grate gives to the building S X f X P B. t. u. 
per hour, there will be the following ratio between the 
heating surface and grate surface: 

H. 8. Efp 

(48) 



G. S. K tz 

Application. — With K tz — 2500 (Trans. A. S. H. & Y. E., 
Vol. XII, p. 133; also, Jo-ur. A. S. H. & Y. E., Jan. 1916) and the 
same notations as in Art. 60. 

H. 8. .6 X 14000 X 5 
■ = = 17 



G. S. 2500 

In practice this ratio varies anywhere betwen 12 and 30. 

From investigations by the Federal Furnace League (now 
The National Warm Air Heating and Ventilating Association), 
furnaces showed an average of 1^/^ square feet of direct 
heating surface and 1 square foot of indirect heating sur- 
face, making a total of 2i/^ square feet of average heating 
surface per pound of coal burned in the furnaces per hour. 



86 HEATING AND VENTILATION 

In the tests of these furnaces combustion rates as high as 
eight pounds of coal per square foot of grate were obtained. 
At this rate of burning the ratio of the heating surface to 
the grate surface is 20 to 1. It is the opinion of the author 
that although good service is obtained in tests by combus- 
tion rates as high as eight pounds, furnaces should be 
selected at a lower value, say five pounds. 

62. Application of the Above Elquations to a Ten Room 
Residence: — In every design, complete calculations should 
be made and the results tabulated for easy reference and 
comparison. Such a tabulation is shown in Table XII, which 
gives all the calculated quantities (in some cases modified 
to suit standard sizes) necessary in the installation of the 
furnace system illustrated in Figs. 17, 18 and 19. The value 
of condensing the work in this way facilitates checking and 
the detection of errors. P"'or satisfactory use plans should 
be drawn to scale and accompanied by sectional elevations. 
The scale should be large enough to be convenient in pro- 
ducing and so the drawings may be easily read. Locate the 
building with reference to the compass points and state ceil- 
ing heights and the principal dimensions of each room. The 
beginner will experience some difficulty in the calculations 
in making proper allowances where absolute values are not 
obtainable, such as exposures, ceilings, fioors, closets and 
smaller rooms where heat is not provided for. The personal 
element enters into this part of the work very much and a 
thorough practical experience is of great value. 

In estimating O the simplest and most convenient 
method is to take it the full area of the sash. That is to 
say, take the full window opening as glass. Values of A' 
for glass have been quoted from .9 to 1.25 by various author- 
ities. It is the opinion of the author that where the full w^in- 
dow opening is used as glass it will be best to make if r= 1. 
In Tables VI and XII this value is used. Referring to the 
Living Room, adding four inches to the width and five inches 
to the height of each window gives 73 X 52 and 73 X 32 
inches respectively = 42 square feet total. 

Floor registers are shown on the first floor plans but 
these may be shifted to wall registers if preferred. Tabula- 
tions in Table XII sho\v vent registers and ducts in each 
room. These values may be used for return registers and 
ducts also. Return lines should be run from each second 
floor room excepting Bath; also from Study, Dining Room 



FURNACE HEATING 87 

and Reception Hall on the first floor. Increase the size of 
the return register in the Hall from 12-in. x 18-in. as calcu- 
lated to 16-in. X 20-in. and omit the return in the Living 
Room. Vent registers should be run to the attic from the 
Bath Room and Kitchen and from such other rooms as de- 
sired by the owner. 

Where the calculated area of stacks is too great to be 
included between the studs of a 4-inch wall, a 6-inch wall 
should be put in. Stacks on the first floor are omitted and 
where wall registers are used, a floor-wall type is recom- 
mended. 

The heat line to the Bath Room is a very bad arrange- 
ment but is about the best that can be done with the present 
room plans. To overcome the effects of the cold wall and 
the resistance of the offset in the floor, set the stack in an 
offset within the Kitchen and enter and leave the floor hori- 
zontal by a good sized turn. Avoid sharp corners. 

In selecting the various stacks and leaders it may be 
well to standardize as much as possible and avoid the extra 
expense of installing so many sizes. This can be done if 
the net area is not sacriflced. 

Diameter of grate allowing ventilation for ten people = 
26 inches. Cold air duct = 600 square inches = 20 X 30 
inches. 



References. — Trans. A. S. H. & Y. E.. Rational Methods 
Applied to the Design of Warm Air Heating Systems, Vol. 
XXI, p. 389. Engineering Data for Designing Furnace Heat- 
ing Systems, Vol. XXI, p. 519. 



HEATING AND VENTILATION 

TABLE XII. 

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1=1 




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114 


192 


198 
138 


390 
120 


168 

180 


246 
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103 
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148 
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99 


129 


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140 


105 


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90 


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FURNACE HEATING 




isihafL I 



32 -7 



Foundation Pl^n 

Ceiling 7' 

Fig-. 17. 



90 



HEATING AND VENTILATION 




Fig-. 18. 



FURNACE HEATING 



91 




Second Floor Plan 

N cEiune 9' 



Fig-. 19. 



92 HEATING AND VENTILATION 

63. Determination of tlie Best Outside Temperature to 
Use in Design and the Costs Involved in Heating by Fur- 
naces: — As a basis for the work of the heating and ven- 
tilating- engineer it is necessary that he be well acquainted 
with the temperature conditions in the locality where his 
services are employed. He should compile a chart showing 
extreme and average temperatures covering a period of 
years and with this chart a fairly safe estimate may be 
made upon the costs involved in operating any heating and 
ventilating system during any part of the average season 
or throughout the entire heating season. Any estimated 
costs of operation are only illustrative of method and prob- 
ability. All one can say is that if the temperature in any 
one season averages what is shown by the average curve for 
the period of years investigated, the cost in operating the 
system may be easily shown by calculation. Heating costs 
are relative values only and cannot be determined exactly 
except under test conditions. 

The heating engineer should also know the minimum 
outside temperatures covering a period of years in that 
locality to determine an outside temperature for his design 
work. Every design is a compromise between average and 
extreme conditions, approaching the extreme rather than the 
average. Patrons expect heating systems to be designed to 
give normal temperatures in the rooms on all but a few of 
the coldest days. Extremely low temperature conditions 
have a duration of from two to three days and it w^ould not 
be good engineering from an economic standpoint to design 
the system large enough to heat to normal inside tempera- 
ture on the coldest day experienced in a period of years. 
The plant would be too large and would require too much 
financial input. As an illustration of the method of obtain- 
ing the outside temperature to be used in design, also meth- 
ods of determining approximate costs for heating, see Fig. 
20. The low central curve is plotted from the average tem- 
peratures on each of the days respectively between Septem- 
ber fifteenth and May fifteenth, covering a period of thirty 
years, at Lincoln, Nebraska. The minimum temperature for 
December, 1911, and January, 1912, (regarded as a period of 
unusual severity) are included. Referring to the chart it 
will be seen that this cold period reached its minimum tenir 
perature of — 26° on January twelfth. Assuming this curve 
to represent the most severe weather in this locality, a study 



FURNACE HEATING 



93 



of conditions may easily determine the best outside tempera- 
ture to be used in design. There were twenty days when 
the temperature was below zero, twelve days below — 5°, 
six days below — 10°, two days below — 20°, and part of one 
day below — 25°. Each of the extreme and sudden drops 
were such as to last from two to three days and were only 
experienced in two or three instances. It is very evident 
that a system designed for 0° outside would fall short of 
the requirement even when put under heavy stress. On the 
other hand one designed for — 25° outside would actually 

TEMPERATURE-CHART-AND-HEAT-LOSS-FOR-AVERACE-YEAR. 

SEPT OCT NOV DEC JAN FEB MAR APR MAY 

160 
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come up to its capacity for only a part of one day out of 
the 240 heating days. One designed for — 10° would fulfill 
conditions without forcing excepting at two or three periods 
of very short duration, at which times the system could be 
forced sufficiently without detriment. The personal equa- 
tion enters into the calculation of the heat loss somewhat 
and there will be some difference of opinion concerning 
which to use, — 10° or — 15°. Probably the latter would be 
a safer value. All that is necessary is to plan for ample 



HEATING AND VENTILATION 



service at all but one or two of the cold periods of short 
duration and the system will be considered very satisfactory 
froin the standpoint of size and capacity. Any additional 
amount put in w^ould be an investment of money which is 
scarcely justified for the small percentage of time that this 
additional capacity would be called for. 

After the minimum outside temperature has been de- 
cided and the plant is desig"ned one would like to know the 
probable expense in handling such a plant throughout the 
heating season. Assume an inside temperature throughout 
the building of 70°. Combine the two half months, September 
and May, into one month, and take the average of these 
average temperatures for the days of each month, thus giv- 
ing the drop in temperature between the inside and the out- 
side of the building. The heat loss from the building la 
approximately proportional to these drops in temperature. 
In this case the differences are as follows: 

September + May 7° below 70° 

October 17° below 70" 

November 32.3° below 70° 

December 44° below 70° 

January 48.7° below 70° 

February 45° below 70° 

March 34° below 70° 

April 19.5° below 70° 

Taking the sum of all these differences as the total, 100 per 
cent., and dividing each individual difference by the total, 
we. have the percentages of loss for the various months as 
follows: 

September + May.... 2.84 per cent, of total yearly loss 

October 6.86 

November 13.05 

December 17.77 

January 19.67 

February 18.20 

March 18.71 

April 7.90 



Total 100.00 

These percentages of loss indicate what may be expected 
in the expense for coal for the respective months of the 
average heating year in the locality stated. Upon this 



FURNACE HEATING 



95 



basis, Fig-. 20 represents an application of the above to a 
residence having a heat loss, H, approximating 100000 B. t. u. 
per hour. The results are shown in B. t. u. loss and in tons 
of coal per year, assuming that the entire house is heated to 
70° upon the inside for each hour between September fif- 
teenth and May fifteenth. The lowest curve is that for 
direct radiation only. The next superimposed curve assumes 
outside air for ten people. The third curve assumes one-half 
of the required air to be recirculated and the upper curve 
assumes all the air to be from the outside. 

64. Filtering, Washing and Humidifying Furnace Air: — 
Two objections frequently urged against indirect heating 
are the dust content and the dryness of the circulated air. 
It is possible to overcome both of these objections in the 
larger mechanical plants, but in small furnace plants where 
the circulated air moves wholly by convection but little 
progress has been made. Cheesecloth screens, fibrous ma- 
terial such as unbraided ropes, linen strips and soft wicking, 
kept moist by water drips, may be used for filtering. To 
offset the air resistance due to the filter, the cross sectional 
area of the duct at the filter should be at least four times 
the net area of the duct, for cheesecloth and fibrous mate- 
rial, and twice the net area for linen strips and wicking. 
The filter should be frequently cleaned by fiushing. Where 
water pressure from city supply or pump is available, sprays 

are more satisfactory than the filter. The essentials 
jj of a small residence air washing plant are: 

pressure water supply, electric current, wash- 
ing chamber and drain- 



^^-fe^^^ 



age. Fig. 21, 



shows 




96 



HEATING AND VENTILATION 



a simple arrang-ement. Having- given a furnace heating 
plant, provide an air mixing chamber for the fresh and recir- 
culated air, install a spray head (a i^- or %-inch pipe built 
in the form of an ell or tee, with the ends plugged and the 
bottom drilled with g^-inch holes), from this spray head sus- 
pend unbraided ropes, hemp strands, linen strips, wicking 
or layers of cheesecloth kept wet by water drips and com- 
pel the air to weave its way through these wetted surfaces 
to the furnace. Much of the dust and other inechanically 
suspended particles in the air will be deposited on the 
fibrous material and finally washed to the sewer. Because 
of the low pressure head moving the air in such a plant no 
unnecessary resistances should he put in. The chief objection to 
the system shown is the water waste which may be any 
amount, from just enough drips to keep the eliminators 
moist, to the full jet outlet under pressure. Water waste 
may be almost wholly eliminated by catching it in a metal 
basin and recirculating it by means of a small electric pump, 
as in Fig. 21, 6. But here again is the expense of operating 
the electric motor and the cost of the small amount of water 
that is thrown away when flushing and refilling*. The oper- 
ating expense in any of these systems is not excessive as 
shown under the application. Where air washing is not con- 
sidered, humidity conditions may be cared for by evaporating 

pans as suggested by 
Figs. 22, («) and (Z>). 




Fig. 22 



Application. — A ten-room residence circulating not to ex- 
ceed 100000 cubic feet of air per hour has a fresh air duct 
(or recirculating duct) 4.2 square feet in cross-sectional 
area. Because of the resistance offered to the circulating 
air let the area be 16 square feet at the filter, say 4-ft. x 4-ft. 
Let the spray head be a single line 4 feet long with ten, 
BV-inch holes on the under side. What will it cost to operate 
such a washing plant for a day of 15 hours under maximum. 



FURNACE HEATING 97 

water flow by each of the two systems, i. e., the waste water 

system, where the water is run to the sewer continuously, 

and the recirculating- system where the only loss is that due 

to occasional flushing-. City water may be assumed to have 

a pressure of 50 pounds per square inch and to cost 15 cents 

per 1000 g-allons. Electric current may be had for 10 cents 

per K. W. At a gage pressure of 50 pounds, a sV-inch hole 

will jet approximately one cubic foot of water (62.5 lbs.) per 

hour. Ten holes, therefore, will waste to the sewer 625 

75 

pounds (75 g-als.) per hour. This water will cost 15 X = 

1000 
1.125 cents per hour, or 16.8 cents for a 15-hour day. 

The electric motor pump may be made to circulate a 
sufficient amount of water without waste, at a pressure 
much less than 50 pounds. For comparative values in cal- 
culation call the pressures the same. With an efficiency of 
the motor pump 40 per cent., the work done per hour by the 
motor is (625 X 50 X 2.3 X .746) ^ (33000 X 60 X .40) = 
.068 K. W. At ten cents per K. W. this is .68 cent per hour 
or 10.2 cents for a 15-hour day. No allowance is here made 
for the small amount of friction loss in the nozzles and 
pipes as these vary g-reatly with the ainount of pipe and the 
pressure under which the system is run. The amount lost 
in evaporation is the same in each case. 

In the two estimated values, that for the waste water 
system would probably decrease in the averag-e plant be- 
cause of a saving- of water by throttling- the supply, while 
that for the pumping- plant would probably increase slig-htly. 
A very fair estimate in either case is one cent per hour for 
maximum service. This is sufficiently larg-e to allow for a 
material increase in the number of the jets above that g-iven. 

Where an electric motor pump is used to circulate the 
water or where the city supply is used without throttling-, 
t'he filters may be omitted, the duct may be uniform in sec- 
tion and the spray head may be located across the bottom of 
the opening- with the holes pointing- toward the top of the 
duct. In this way the spray is broken up by contact with 
the deflector at the top of the duct and falls as a mist 
throug-h the air current. 

It would be of interest here to briefly discuss the prot- 
cible temperature and humidity effects upon the circulating- air 
within the residence if a washing- plant of this character 
were installed. This section is offered as a fair probability 



98 HEATING AND VENTILATION 

in the absence of collected data. For basis of argument, 
assume the following: 100000 cubic feet or air circulated 
per hour at the register, register temperature 120°, no re- 
circulated air used, temperature outside 50°, temperature 
inside 70°, humidity outside 50 per cent., humidity inside 45 
per cent. What amount of water is absorbed per hour? 

100000 cubic feet of air at 120° at the register is equiv- 
alent to 87930 cubic feet at 50° on the outside and 91380 
cubic feet at 70° in the room. The amount of moisture in a 
cubic foot of saturated air on the outside at 50° is 4 grains 
and at 50 per cent, saturation would.be .50 X 4 = i2 grains. 
Correspondingly in the room air at saturation we have 7.98 
grains and at 45 per cent, humidity .45 X 7.98 = 3.59 grains. 
The total amount of moisture in the incoming air is 87930 X 
2 = 175860 grains (25.12 lbs.) per hour. The total amount 
of moisture in the room air is 91380 X 3.59 = 328054 grains 
(46.8 lbs.) per hour. It is evident that the difference be- 
tween these two amounts (46.8 — 25.12 = 21.73 lbs.) has 
been added per hour from the washing water (See Art. 27). 
In this way the weight of water absorbed may be worked 
out theoretically for any temperatures and for any humidities. 
The actual amounts absorbed, however, may vary consider- 
ably from the theoretical figures because of the wide range 
in temperatures and humidities between the incoming and 
outgoing air and the shortness of time the air is in actual 
contact with the water. 

Close regulation of the humidity of such a plant is a diffi- 
cult problem. The humidostat, if used, necessarily acts to 
control the amount of water flowing. When the humidity 
is high this cuts off the flow^ of water, in which case the 
apparatus ceases to serve as a washer. From what is 
known of such plants it is probable that the humidity of 
the air after passing the furnace is never high enough to 
give much concern and the humidostat may be eliminated. 
The location of the spray head, in the cool air chamber, re- 
tards the absorption process because cool air takes up 
moisture with less freedom than warm air. Even assuming 
that the cool air is fully saturated as it enters the furnace, 
the humidity will drop so rapidly as the air is heated that 
there will never be any danger of depositing moisture on 
the furniture of the room. To illustrate. — In the above 
problem assume that the 50° air is saturated as it enters 
the furnace (a condition it will seldom reach). When heated 



FURNACE HEATING 99 

to 70° the humidity will be 52 per cent., which is a very sat- 
isfactory amount. Again, if the outside air is 60° and sat- 
urated as it enters the furnace, the humidity, w^hen raised 
to 70° will be 75 per cent., an amount that would still cause 
the air to be agreeable. Now what happens at low tempera- 
tures? If the entering- air is saturated at 40°, the humidity 
at 70° would be 37 per cent. From this it would seem 
that a humidostat, for the purpose of controlling the moist- 
ure, would be of very little service unless the air were cir- 
culated for purposes of ventilation at or near 70° and satura- 
tion, a state of affairs very seldom asked for in residence 
work. 



CHAPTER V. 



FURNACE HEATING AND VENTILATING. 



SUGGESTIONS ON THE SELECTION AND INSTALLATION 
OF FURNACE HEATING PARTS. 

65. The Furnace; — Furnaces for residences are usually 
of the portable type, illustrated by Fig-. 23. This consists of 
a heating- stove enclosed in a shell composed of two metal 
casing-s having- a dead air space or an asbestos insulation be- 
tween them. Some of the larg-er furnaces used in the larg-er 
residences, small schools, etc., have permanent casem.ents 
of brick work as in Fig-. 24. Both types of furnaces g-ive 




Fig- 



g-ood results. The points usually g-overning- the selection be- 
tween portable and permanent setting-s are required capac- 
ity, price and available floor space. 

The stoves are made of cast iron, wroug-ht iron and 
steel. The cast stove admits of a g-reater variety of shapes 
than those made of rolled plates hence it is more commonly 



FURNACE HEATING 



101 



used. The sections are assembled with cemented joints 
while the rolled sections are riveted. The chief objection 
to the cast stove is the frequent leakage of fuel gases from 
the combustion chamber to the warm air passages. In a 
properly designed and set up cast furnace there should be 
little excuse for leakage. When it does occur, examine the 
cement in all the joints especially around the door openings. 
It is claimed by some that the heated cast iron plates permit 
the passage of some of the gases directly through the metal. 
While this may be true to a certain degree in comparison 
with rolled materials such as steel, there is little doubt that 
practically all leakage can be traced to cracked sections or 
to broken cement joints. In general, the fewer the joints 




Fig. 24. 
in a furnace stove the better. On the other hand cast iron 
corrodes less than rolled plate and the heavy cast walls of 
this type act as a storage for heat and tend toward less 
fluctuation of air temperature. 

Furnaces are direct-draft and indirect-draft. In the direct- 
draft type the radiator (heat distributor) is above the fire 
and the gas passages are usually short and fairly direct to 
the chimney. In the indirect-draft type the radiator is be- 
low the fire and the gases are first deflected downward over 
the radiator and then upward to the chimney. In this type 
there should always be a by-pass, properly dampered, so 
that wh«n there is a lack of draft due to a cold chimney 



102 HEATING AND VENTILATION 

(usually found when starting a new fire) or other cause the 
g-ases may be given a short cut to the chimney removing 
excess friction and avoiding smoking. An indirect-draft 
furnace should be used only on a protected or enclosed chim- 
ney. In cases where sufficient draft is sure at all times this 
type of furnace is probably the most economical. 

The cylindrical fire pot is better than a conical or spher- 
ical one, there being less danger of the fire clogging and 
becoming dirty. A lined fire pot is better than an unlined 
one, because a hotter fire may be maintained in it w^ith less 
detriment to the furnace and less contamination of the air 
supply. There is a loss of heating surface in the lined pot, 
however, and in most furnaces the fire pot is unlined to ob- 
tain this increased heating surface. 




Fig. 25. 

Some form of shaking or dumping grate should be se- 
lected, as a stationary grate is far from satisfactory. Care 
should be exercised in the selection of the movable grate, 
as some forms not only stir up the fire but permit much of 
it to fall through to waste when being operated. 

In most furnaces the fuel is fed to the fire pot from a 
door above the fire. These are called top-feed furnaces. In 
some forms the fuel is fed up through the center of a rotary 
ring grate. These are called under-feed furnaces (Fig. 25) 
and for the finer grades of coal are preferred to the top-feed 
furnaces. 

The size of the furnace for any given work may be ob- 
tained from the estimated heating capacity in cubic feet of 



FURNACE HEATING 



103 



room space as given in Table 20, Appendix. A better and 
safer way, and one that serves as a good check on the 
above, is to select the furnace from the calculated grate area 
(See Art. 60). 

A comhinaticn furnace and heater is shown in Fig. 26. With 
it some of the rooms of a residence may be heated by warm 
air and the remainder by hot water or steam. In this way 
rooms to be ventilated as well as heated may be connected 
by the proper stacks and leaders to the warm air deliveries, 
while rooms requiring- less ventilation or heat only, or those 
rooms that are difficult to heat with air circulation may 
have radiators- installed and connected to the flow and re- 
turn pipes of the water or steam system. 




Fig-. 26. 



Pipeless furnaces are manufactured and installed in stores, 
small residences and the like. In this type the stove is sur- 
rounded by two independent casings instead of one as in the 
pipe furnace, heated air circulating upward between the 
stove and the inner casing and return air downward between 
the casings. The top of the furnace terminates in a short 
stack capped by a combination hot-and-cold air register at 
the floor line of the flrst floor room. The central zone of 
the register supplies air to the room and the outer ring zone 



104 



HEATING AND VENTILATION 



carries cold air from the room to the furnace. All air is de- 
livered to one room and from here circulates to and from 
the other rooms of the house through transoms, open doors, 
etc. Fig-. 27 shows the principle of operation. Compared 
with other furnace plants the application of this type is 




Fig. 27. 



much simpler and the installation cost is less. Its satis- 
factory application is limited to those buildings having open 
interior construction where the furnace may be centrally 
located and where every room has continuous opening to the 
room above the furnace. Furnaces of this type are good 
heaters but have no ventilating possibilities. One of the 
objections usually found with this type of furnace is the 
presence of floor drafts in the room above the furnace. Since 
bath rooms, toilet rooms, laundries and kitchens are usually 
not connected to the return circulation, these rooms are dif- 
ficult to heat from the pipeless furnace. 

Room Heaters (slightly modified forms of standard fur- 
naces) may be obtained for use in small buildings having no 
basements. Such furnaces should have well insulated metal 
jackets to protect the nearby room furnishings from exces- 
sive heat. The circulating air may be taken from the out- 



FURNACE HEATING 105 

side of the building- in about the same way as a direct-in- 
direct radiator (See Art. 102), or may be recirculated from 
the room, entering the bottom of the furnace at the floor 
line through a register base, and leaving from the wide 
open top of the furnace. A vent flue for the room is usually 
provided by the side of or in connection with the chimney or 
smoke flue. Room heaters are naturally not desired be- 
cause of their appearance but they are effective heaters and 
where properly installed may give fair ventilating effect. 
The one serious objection to the room heater, other than its 
appearance, is the presence of floor drafts as in the pipeless 
furnace. 

One of the most important points in the selection of any 
furnace is its cleaning possibilities. If there is a probability 
that soft coal may be used at any time the furnace should 
be provided with clean-outs so situated that all parts of the 
gas passages may be reached by flue swabs. 

Care must be exercised also in the installation of the 
furnace to protect the nearby combustible material from 
fire. Smoke pipes, especially, must have ventilated thimbles 
giving- at least 2-inch air space all around the pipe where 
passing through combustible walls. 

66. liocation and Setting of the Furnace: — A furnace 
should be set as near the center of the house plan as pos- 
sible. Where this can not be done, preference should be 
given to the colder sides (sides subjected to the heaviest 
winter winds), in most localities the north and west. In 
any case, it is advisable to have the leader pipes of uniform 
length and pitch if possible. The smoke pipe should be 
short, but it is better to have a moderately long smoke pipe 
and obtain a more uniform length of leaders than to have a 
short smoke pipe and leaders of widely different lengths. 

The furnace should be set low enough to give a good 
upward slope to the leaders from the furnace to the respec- 
tive stacks. This should be not less than one inch per foot of 
length and more if possible. Each leader should be dampered 
near the furnace. 

The location of the furnace will call forth the best 
judgment of the designer, since a right or wrong decision 
here is very vital. 

Foundation. — All furnaces should have the manufactur- 
er's directions to govern the setting-. Such information la 



106 



HEATING AND VENTILATION 



usually folloAved. In every case the furnace should be 
mounted on a level, brick or concrete foundation especially 
prepared and well finished with cement mortar on the inside, 
since this interior is in contact with the fresh air supply. 

67. Fresh Air Duct: — Ducts below the floor are best 
constructed of hard burned brick walls 4 inches thick, con- 
crete walls 2 to 3 inches thick or vitrified tile; the floors to 
be not less than 1-inch concrete and the tops to be 1- to 2- 
inch concrete slabs. The walls and floors of the brick or 
concrete ducts should be smooth plastered with neat cement 
and all joints should be tight. 

Ducts above the floor are usually made of galvanized 
iron. Where made of boards they should be solid material 
well tongued and grooved. The riser from the main hori- 
zontal to the outside of the building may be of wood, tile 
or galvanized iron and the fresh air inlet should be ver- 
tically screened. The whole fresh air line should have tight 
joints and should be so constructed as to be free from sur- 
face drainage, dirt, rats and other vermin. 

i; 




E5H A!R RETU 




TURN 



FRONT 



FRONT 

Fig. 28. 



FRONT 



In addition to the opening for the admission of the 
fresh air duct, another opening or openings may be made 
under the furnace for the purpose of admitting the duct 
which carries the recirculated air from the rooms to the 
furnace (See Fig. 28). Occasionally the two ducts unite in 
a Y fitting before entering the furnace, in w^hich case the 
fitting should be so constructed as to make the two uniting 
streams of air enter as nearly parallel as possible. Each of 
these ducts should have adjustable dampers so as to make 
them independent of the other. Each duct also should be 
provided with a door that can be opened temporarily to the 
basement for inspection and cleaning. Sometimes it is de- 



FURNACE HEATING 



107 



sirable to have two or more fresh air ducts leading- from 
the different sides of the house to g-et the benefit of any 
change in air pressure on the outside of the building (See 
also Figs. 16 and 17). 

Arrangements may be made for pans of clear water in 
the air duct entering the furnace (See Art. 64) to give 
moisture to the air current, but it should be understood that 
only a small amount of moisture will be taken up at this 
point from still water surfaces. In most cases where mois- 
tening pans (commonly called water pans) are used, they are 
installed in connection with the furnace itself. Furnaces 
should have special means provided for moistening the cir- 
culated air. The water pan is a step in the right direction, 
but this alone is not sufficient (See Art. 27). 

68. Recirculatinj^ Ducts: — Ducts should be provided 
from the rooms within the building", through the basement 
to the bottom of the furnace. These ducts carry the air from 
the rooms back to the furnace to be reheated for use again 
within the building. Recirculating the air gives a more positive 
type of heating system. Rooms difficult to heat without recir- 
culation are improved with its use and rooms at a distance 
from the furnace should always have it. Freqiiently a num- 
ber of rooms are grouped together on one return line. Small 
residences may have but one return line leading from the 
return register in the front hall near the door. Return lines 
should be grouped in the base- 
ment to simplify the system and 
to avoid making- many openings 
into the furnace foundation. Re- 
turn stacks should be light tin or 
galvanized iron built-in between 
the studding of the outside walls 
and need not be insulated. Con- 
tractors usually omit these metal 
ducts between the studs, and the 
dust from the rooms settling- on 
the roug-h surfaces of the studs 
and sheathing makes an unsani- 
tary condition. In like manner 
horizontals in the basement are 
frequently slighted by tinning un- 
der two adjoining- joists thus 
Fig. 29. forming the duct. Such construe- 




108 



HEATING AND VENTILATION 



tion should not be permitted. All vertical return lines and all ex- 
posed horizontal runs between the return registers in the rooms and 
the attachment at the furnace, should be tin or galvanized iron with 
tight joints. (See Fig. 29). Avoid overhead return ducts near 
the furnace. In some installations it is necessary to carry 
these ducts along- the basement ceiling part way across the 
basement but the drop to the floor should be made at such a 
distance from the furnace that the air in the vertical return 
vi^ill not be retarded in its fall by the heat from the furnace. 
69. Leaders: — All leaders should be round and free 
from unnecessary turns. They should be made from No. 24 
or No. 26 galvanized iron or tin, should be run as straight 
as possible and should be well supported. Connections with 




Fig. 30, 
the furnace should be straight, but if a turn is necessary, 
provide long radius elbows. All connections to risers or 



FURNACE HEATING 



109 



stacks should be made through long radius elbows. Rec- 
tangular shaped hoots having attached collars are frequently 
used but these are not satisfactory because of the impinge- 
ment of the air against the flat side of the stack; also, be- 
cause of the danger of the leader entering- too far into the 
stack and shutting off the draft. Leaders should connect to 
first floor registers by long radius elbows. Leaders should 
have as few joints as possible and these should be made firm 
and air tight. Fig. 30 shows different methods of connecting 
between leaders and stacks, and between leaders and regis- 
ters. 

Leader pipes should be covered to avoid heat loss and to 
provide additional safety to the plant. The covering usually 
put on is one or two thicknesses of asbestos paper laid with 
face contact. As a heat insulator this is little better than 
the bare pipe. A better way is to have the layers of as- 
bestos paper separated by spiral wrappings of w^ire, air cell 
material or mineral wool to give dead air spaces. Leaders 
passing through combustible walls must have ventilated 
thimbles, giving at least a 1-inch air space all around the 
leader. 

70. Register Connections: — The most efficient first floor 





Fig. 31. 



warm air intake is through a floor register. Fig. 31a shows 
a galvanized floor box enclosing a floor register and con- 
nected to the leader by a round elbow. Floor registers give 



110 



HEATING AND VENTILATION 



the freest circulation that can be obtained in first floor fur- 
nace heating-, but they are dust catchers and unsanitary; 
also, in rooms having hard wood floors and special furnish- 
ings they are not usually permitted. In such cases the floor- 
wall register may be used as in Fig:. 31 &. This type has a box 
and leader opening- much larger than is possible with a wall 
stack and compares favorably with the floor type. The ap- 
pearance of the floor-wall register as a feature of the room 
furnishings and its sanitary qualities are enoug-h better than 
the floor type to justify its general use. On the second floor 
a stack is necessary and the wall register is g-enerally used 
(.Fig-. 31 c). Where these are installed the upper end of the 
stack should terminate in a quarter turn to throw the warm 
air toward the room and avoid eddy currents at the dead end. 
All intake reg-isters to the rooms and vent reg-isters 
leading- to the attic should be provided with shutters. Re- 
turn lines may have register faces only. For larg-e reg-ister 
faces where streng-th is not an important factor, g-rilles 
made from latticed wood strips are fre- 
quently used. Fig-. 31 cl shows one of these 
under a hall seat. For calculations and 
sizes of registers see Arts. 53-55, and 
Tables 19 and 21, Appendix. 

71. Stacks or Risers: — The vertical air 
pipes leading- to the registers are called 
stacks or risers. They are rectang-ular in 
section and are usually fitted within the 
wall (See Fig-. 32). The size of the stud- 
ding- and the distances these are set, cen- 
ter to center, limit the effective area of 
the stack. All stacks should be insulated 
to protect the woodwork. This is done by 
making- the stack small enough to clear 
the woodwork by at least l^-inch and then 
wrapping- it with some nonconducting ma- 
terial such as asbestos paper or hair felt 
held in place by wire. Patented double 
walled storks having- an insulating- air space 
between the walls are more nearly fire- 
proof. All stacks should have tight joints and should have 
ears or flaps for fastening- to the studding. Patented stacks 
are made in standard sizes and of various lengths. Sizes or- 
dinarily used in practice are given in Table 17, Appendix. 




Fig. 32. 



FURNACE HEATING 111 

A stack is sometimes run up in a corner or in some re- 
cess in the wall of a room where its appearance, after being 
finished in color to compare with that of the room, Is not 
unsightly. This is necessary in any case where the stack 
is installed after the building is finished. It is also pre- 
ferred by some because of its additional safety and because 
more stack area may be obtained than is possible when 
placed within a thin wall. 

All stacks should be located in or near partition walls 
looking toward the outside or cold side of the room. This 
location protects the air current from excessive loss of heat, 
as would be the case if placed in the outside walls. It also 
provides a more uniform distribution of the air from the 
furnace. 

The area of the stack best adapted to any given room 
should not be taken by guess (See Art. 56). In a great 
many cases the architect specifies light partition walls be- 
tween large upper rooms, say 4-inch studding set 16-inch 
centers between 12-foot by 15-foot rooms, heavily exposed. 
Prom the theoretical calculations of heat losses, these rooms 
require larger stacks than can be placed between studding 
as stated, but it is very common to find such rooms provided 
for in this way. One possible excuse for such practice may 
be the fact that most second floor residence rooms are de- 
signed for sleeping rooms and not for living rooms. Regard- 
less of this fact, however, it would be well to provide for 
all emergencies and follow the rule that every room should he 
provided loith facilities for heat as if it xcere to de used as a living 
room in the coldest weather. If this were done there would be 
fewer complaints of defective heating plants and less mi- 
grating from one side of the house to the other on cold days. 

Lack of heating capacity for any one room may be over- 
come by providing two stacks and registers instead of one. 
This plan will he fairly satisfactory since one of the regis- 
ters may be shut oiT in moderate weather. It requires an 
additional expense, however, which is not justified. A better 
way is to provide partition walls of greater thickness or 
specially planned-for stack openings, so that ample stack 
area may be put in. The ideal 'conditions will be reached 
when the architect anticipates the heating requirements and 
provides air shafts of sufficient size to accommodate round 
or nearly square stacks. 



112 



HEATING AND VENTILATION 



Single stacks are sometimes used to supply air to two 
adjoining rooms. Such stacks have metal partitions extend- 
ing down a few feet from the upper end to split the air cur- 
rent and direct it to the rooms. This practice is question- 
able because of the liability of the pressure of air in the 
room on the cold side of the house forcing the heated air 
around the partition to the other room. Also, single stacks 
are frequently used to supply roonas one above the other. 
This is not satisfactory except where the regulation in each 
room is taken care of by the same person. When the upper 
register is full open it will rob the lower register and when 
the lower damper is full open the upper room gets no heat. 
A better method is to install a separate line for each room to 
be heated. 

Vent stacks should be located in the inner or partition 
walls and should lead to the attic. If it is thought neces- 
sary, they may there be gathered together in one duct lead- 
ing to a vent through the roo^. It is an ideal arrangement 
but not always necessary to have a vent stack in every 
room. Some rooms, from their location, are easily ventilated 
without them. Bath rooms, toilets, laundries and kitchens, and 
rooms near the center of the house should ahoays have independent 
ventilation. In any rooms where nat- 
ural ventilation is an important fea- 
ture, vent ducts to the attic should 
have two tappings, floor and ceiling, 
each provided with shuttered regis- 
ters. The floor vent should be used 
on cold days to economize the heat 
, _ i| \ p I and the ceiling vent should be used 

l^^l \ I 1,^ on warm days. Such a system of 

ventilation may be used in connec- 
tion with direct-indirect radiators in 
Fig. 33. small schools (See Fig. 33). 

73. Air Circulation Within the Room: — The location of 
the heat register relative to the vent register, will determine 
to a great extent the circulation of air w^ithin the room. 
Fig. 34 a, &, c, and d, shows the effect of the different loca- 
tions in forced circulation. The best plan, from the stand- 
point of heating, is to enter the air at a point above the. 
heads of the occupants and withdraw it from the floor line, 
at or near the same side from which the air enters. This 




FURNACE HEATING 



113 



\V1|'/ 
Oh* 





Fig-. 34. 



gives a more uniform distribution as shown by the last 
fig-ure. It is doubtful, however, if tliis metliod will give the 
best ventilation in crowded rooms where the foul air nat- 
urally collects at the top of the room. Circulation in fur- 
nace heating is not as satisfactory as in other forms of in- 
direct heating. Air usually enters the room from the floor 
or the inner wall near the floor line and leaves for recircula- 
tion near the floor line on the opposite or cold side. Circula- 
tion within the room is shown by 6. Where there is no re- 
circulation it leaves through a vent register usually near 
the floor line and located at such a point that the air will 
traverse as much of the room as possible before leaving. 

73. Fan-Furnace Heating System: — In large furnace in- 
stallations where the air is carried in long ducts that are 
nearly, if not quite horizontal and where a positive supply 
of air is a necessity in all parts of the building, a combina- 
tion fan and furnace system may be installed. Such syts- 
tems may be properly designated mechanical warm air sys- 
tems but they should not be confused with the mechanical 
fan-coil systems described in Chapters X to XII. The objec- 
tions urged against the fan-furnace systems are the high 
temperatures of the circulating air and the smoke and dust 
content picked up from the furnace. 

Fan-furnace systems may be set in multiple if desired, 
i. e., one fan operating in connection with two or more fur- 



114 



HEATING AND VENTILATION 



naces. Fig. 35 represents a two-furnace plant showing a 
fan and two furnaces. Air is drawn into the fresh air room 
through a grate in the outside wall and is forced through 
the fan to the furnaces where it divides and passes up 
through each furnace to the warm air ducts. Part of the 
fresh air from the fan is by-passed over the top of the fur- 
naces and is admitted to the warm air ducts through mixing 




Fig. 35. 

dampers. These dampers control the amount of hot and cold 
air for any desired temperature of the mixture. Temperature 
control may be installed and operated with this system. 
Paddle wheel fans (always located between the furnace and 
air intake) are preferred, although the disk wheel may be 
used where the pipes are large and where the air must be 



FURNACE HEATING 



115 



carried but short distances. For fan types see Chapter X. 
74. Hot Air Radiator Systems: — In some localities gas, 
either natural or manufactured, is used as fuel for heating 
purposes. Wherever the supply is available at rates com- 
mercially reasonable, it may be piped direct to radiators 
within the rooms and burned as in ordinary gas stoves, the 
products of combustion being circulated through the radia- 
tors and then exhausted. This is the principle of the Rector 
system (Fig. 36). The gas supply to each burner is under 
double control: first, by a thermostat which maintains con- 
stant room temperature; second, by vacuum produced by the 
exhaust fan which acts as a safety appliance. For thermo- 



Thermostat Q 






aEx/wfiysfer 
Swjfch 




Fig. 36. 
static control see Chapter XIV. For vacuum control, a valve 
in each radiator is so arranged that when the vacuum fails, 
due to the stopping of the fan, gas is shut off from the bur- 
ner, leaving only a pilot light flame. When the vacuum is 
again produced by the starting of the fan, gas is admitted 
to the burner and ignited automatically by the pilot light. 
The products of combustion pass upward to the top and then 
downward through the sections where they are drawn off from 
the bottom central connection by the exhaust fan. No water, 
steam or circulating mediums other than the combustion 
products themselves, are used. The facts that combustion 



116 



HEATING AND VENTILATION 



takes place within the room to be heated, that the only loss 
of heat is that carried off by the exhausting gases and that 
each room is an independent unit give just claim for high 
efficiency in fuel economy. Such a system is practically 
under the control of a push button which starts and stops 
the motor exhaust fan. It is very convenient with its flexi- 
bility and independence of units and is conducive to economy 
under careful management. The calculated radiator sur- 
face is less than that required for steam systems, because 
of the higher average internal temperature. 

Gas radiators should not be placed close to woodwork or 
other inflammable material. In general, advantages such as 
no janitor service, no coal storage spaces, no furnace chim- 
ney, no coal dust and dirt, and no ashes are inherent with 
these systems. They are used in localities having mild 
climates and where continuous firing is not necessary. 

In the Hatvkes system the exhaust fan and the automatic 
gas valve of the Rector system are eliminated. The products 
of combustion pass through radiators similar to those just 




Fig. 37. Fig. 38. 

mentioned but the exhausting of these products is accom- 
plished by connecting each radiator to a stack, or by provid- 
ing a separate 2-inch riser to the roof which acts as a stack 
for that particular radiator. The air necessary for burning 
the gas is admitted through slots near the bottom of each 
section of the radiator. All radiators are operated by hand 
control in the same way as the ordinary gas stove. Fig. 37 
shows the Hawkes ventilating gas radiator as commonly 
installed. 



FURNACE HEATING 



11' 



Hot air radiators heated by gas may also be of the in- 
direct type in which case they are designated gas floor fur- 
naces. Fig. 38 shows one of these furnaces connected to a 
first floor register. The operation is like that of the pipeless 
furnace, Art. 65. Above the furnace is a combination hot- 
and-cold air register which recirculates the room air over a 
gas heated cast radiator. Combustion takes place within 
the cast radiator and the gases are carried by vent pipes to 
the chimney. These furnaces are hand controlled at the 
register. 

75. Fire Hazard: — Protection against fire from heating- 
apparatus is too little considered by the average house- 
holder. Several points in every furnace plant may be con- 
sidered danger points. These are, in the order of impor- 
tance: a loosely built chimney, the top of the chimney too 
close to a steep pitched shingle roof, wood work of the 
house fixed rigidly to the chimney, the smoke pipe from the 
furnace too close to the house framing-, the top of the fur- 
nace unprotected and too close to the joists or basement 
ceiling, and the hot air pipes too close to the wood work. 
Especial care should be taken in protecting gas floor-heaters, 
as described in Art. 74. The ounce of prevention in such 
cases may be easily and cheaply applied, and should be in- 
sisted upon. 



76. Accelerating- Circulation in Furnace Plants: — Many 
furnace plants are not giving satisfaction because of slug- 
gish circulation. This trouble 
which in most cases may be 
traced to defective design, may 
be corrected as in Fig. 39, by 
inserting a 12- to 16-inch disk 
fan in the return duct, prefer- 
ably below the inlet point of the 
outside air. The fan may be 
run when warming up the house 
in the mornings and at times of 
severe weather. This may be 
connected to the average lamp 
socket and will cost from % to 
1 cent per hour depending upon 
the electric prices in the locality. 




118 HEATING AND VENTILATION 

77. Suggestions for Operating Furnaces: — Furnaces are 
desig-nated hard coal and soft coal, depending- upon the type of 
desig-n and the construction of the g'rate, hence the g^rade of 
coal best adapted to the furnace should be used. The size 
of the openings in the grate should determine the size of 
coal used. 

Keep coal in coal pile moist but not wet. 

Clean all furnace g'as passag-es frequently. 

Keep the Are pot well filled with coal and have it evenly 
distributed over the grate, firing- lig-ht and often for best 
service. In a properly desig-ned plant, when necessary, flr- 
ing-s may be as few as three or four per 24 hours and g'ive 
g-ood service. 

Keep the fire free from clinkers. They should be re- 
moved from the fire once or twice daily. It is not necessary 
to stir the fire so completely as to waste the coal throug-h 
the g-rate. With a g-ood chimney draft, some ashes just 
above the grate line will be a benefit in that it will retard 
the fire and tend toward less clinkering-. Clinkers are formed 
with hig-h volatile coals and strong- draft throug'h the g-rate. 
They are avoided ty slow and steady combustion, hy having a thick 
fuel hed of live coals and hy having slow draft through the grate 
(generally draft damper fully closed and small draft above the fire). 
The arrang-ement of these dampers will be determined by 
experience. 

A g-ood sized chunk of wood embedded into the top of 
the fuel bed is a coal saver. 

When replenishing- a poor fire do not shake the fire, but 
put on some coal (or chunk of wood) and open the drafts. 
After the fuel is well ig-nited clean the fire. 

The ash pit should be cleaned each day. An accumula- 
tion of ashes below the g-rate soon warps the g-rate and 
burns it out. Sifting- shovels may be used and the unburned 
coal put back in the furnace. 

Keep all dampers in working- order. 

Have a hand damper in the smoke pipe and keep it open 
only as far as is necessary to create a draft. Check damper 
(opening- to basement air) must not be open unless draft 
damper under g-rate is closed. 

Keep the water pans full of water and all humidity 
apparatus working-. 

Clean the base of the chimney, the furnace and the 
smoke pipe thoroug-hly in all parts at least once each year. 



FURNACE HEATING 119 

Keep the fresh air duct free from rubbish and impurities. 

Allow plenty of pure fresh air to circulate through the 
furnace. In cold weather part of this supply may be cut off. 
When fuel saving- is a necessity, it may be cut off entirely. 

Have the basement well ventilated by means of outside 
wall ventilators, or by special ducts leading to the attic. 
Never permit the basement air to be circulated to the living 
rooms. 

To bank the fires for the night, shake down and clean 
the fire, bank the live coals to one side of the fire box, fill up 
with fresh fuel, sift the ashes and distribute the unburned 
coal on the fire; with a poker make a hole through the fill 
into the live coal bed to permit of some flame above the fuel 
bed, close th6 under drafts and open the fire door draft 
slightly. Caution. — ^Never cover the entire incandescent fuel hed 
toith fresh coal and close the drafts. If this is done, coal gas 
will collect above the fire and will ignite from the first fiame 
that breaks through the fuel bed, causing an explosion. 



CHAPTER VI. 



HOT WATER AND STEAM HEATING. 

DESCRIPTION AND CLASSIFICATION. 

78. Hot Water and Steam Systems Compared ^vith 
Furnace Systems: — Hot water and steam installations are 
more complicated in the number of parts than furnace in- 
stallations; they use a more cumbersome heat carrying 
medium, for which a return path to the boiler must be pro- 
vided; and have parts, in the form of radiators, which 
occupy valuable room space. But the hot water and steam 
plants have the advantage in that the circulation, and the 
transference of heat, are not affected by wind pressures. 
Hot water and steam will carry heat as readily to the w^ind- 
ward side of a house as tb the leeward side, a point which 
is known to be quite impossible with air. Furnace heating 
has the advantage of inherent ventilation, while the hot 
water and steam systems, as usually installed, provide no 
ventilation except that due to air leakage. 

79. Elements of Hot Water and Steam Systems: — Hot 
water and steam systems consist of three principal parts: 
the boiler or heat generator, the radiators or heat distrib- 
utors, and the connecting pipe lines which provide the cir- 
cuit paths for the hot water or the steam. In the hot water 
system it is essential that the heat generator be located at 
the lowest point in the circuit for, as explained in Art. 11, 
the only motive force is that due to convection currents in 
the water. In the steam system this is not essential. The 
water of condensation may or may not be returned by 
gravity to the boiler. Hence, with a steam system a radia- 
tor may be placed below the boiler, if its condensation be 
trapped or otherwise taken care of. 

Concerning piping systems and connections, several 
terms commonly used by heating engineers should be de- 
fined. The large pipes in the basement connected directly 
to the source of heat, and serving as feeders to the pipes 
running vertically in the building, are known as mains.- 
Supply mains are those that carry water or steam from the 
source of heat to the radiators and return mains are those 



HOT WATER AND STEAM HEATING 



121 



that carry water or condensation from the radiators to the 
source of heat. The vertical pipes connecting between floors 
are called risers, while the short horizontal pipes between 
risers and radiators are riser arms or branches. As there are 
supply mains and return mains, so also there are supply 
risers and return risers. A return main traversing- the 
basement above the water line of the boiler is designated a 
dry return and carries both steam and water of condensation; 
one in such position below the water line as to be filled with 
water is designated a wet return. The returns of all two- 
pipe radiators connecting with wet returns are said to be 
sealed. 

80. Classifications: — One classification of hot water and 
steam systems is based upon the position and manner in 
which the radiators are used. The arrangement which is 
most familiar is the one wherein the radiators are located 
within the space to be heated and are surrounded only by 
room air. Radiators so placed (Fig. 40) provide no ven- 
tilation and are designated direct radiatio7i. In direct-indirect 




Fig. 40. 



f^ig. 41. 



radiation the radiators are placed as in direct radiation but 
the lower portion of each radiator is encased and connected 
with the outside air as shown by Fig. 41. The direct-indirect 
system provides certain ventilating possibilities and should 
always be used in connection with inside wall ventilating 
stacks. Indirect radiation is installed remote from the rooms 



122 



HEATING AND VENTILATION 




Fig:. 42. 



to be heated and ducts carry the heated air from the radia- 
tors to the rooms either by convection, or by fan or blower 
pressure. In residence worl<; this radiation is usually sus- 
pended from the basement ceiling as shown by Fig. 42. This 




Fig-. 43. 



HOT WATER AND STEAM HEATING 123 

provides a combination system of steam and indirect warm 
air. When the radiation for an entire building is installed 
in one basement room, and each room of the building has 
carried to it its share of heat by forced air through ducts 
from one large centralized fan or blower, the system is 
called a plenum system or fan-coil system and is given special 
consideration in Chapters X to XII. 

A second classification for hot water and steam systems is 
made according to the method of pipe connection between 
the heat generator and the radiation. The one-pipe basement 
main steam system (Fig. 43) is the simplest in construction 
and is preferred by many for steam installations. As the 
name indicates, its distinguishing feature is the single pipe 
path leading from the source of heat to the radiator, the 
steam and the returning condensation both using this path. 
In the risers and connections the steam and condensation 
flow in opposite directions, thus requiring larger pipes than 
where a flow and a return are both provided. In the mains 
the condensation usually flows with the steam and not 
against it. In the so-called one-pipe basement main hot water 
system (Fig. 49), radiators have two tappings and two risers, 
but the flow riser is tapped out of the top of the single 
basement main, while the return riser is tapped into the bot- 
tom of that same main by either of the special fittings shown 
in section in Fig. 44. The theory is that the hot water from 
the boiler travels along the top of the 

Q „., ^^^M ^^Trm "^^ii^' while the cooler water from the 

mp.....^. .,^.„..,,,,,„ .^^^^^yu^,^ radiators travels along the bottom of 
III' ; : III this same main and two streams re- 

^^\_\^ ■ yymvKw^^^^^^^ main separate. Where mains are short 

and straight as in small residence in- 
stallations, this system seems to give 
satisfaction, but where mains are long 
and more complicated a mixing of the 
„. .. two streams is unavoidable and the 

Fig. 44. 

supply to the farther radiators is 

cooled to such a degree that the system becomes unreliable. 

The two-pipe basement main system (Figs. 47 and 50) is 
standard with both steam and hot water installations. For 
steam work (especially for small installations) it is prob- 
ably no better than the one-pipe system but for hot water 
work it is much preferred. In this system two separate and 



124 



HEATING AND VENTILATION 



distinct paths may be traced from any radiator to the source 
of heat. In the basement are two mains, the supply and the 
return, and the risers from these are always run in pairs, 
the supply riser on one side of a tier of radiators, the return 
riser on the other side. A two-pipe steam system should 
have sealed returns (See Art. 82). 

The attic supply system, or Mills system, has found much 
favor with heating engineers in the installation of the larger 
steam and hot water plants. In this 
system the supply and returns both 
flow downward. This is accomplished 
by first leading the steam or water to 
the attic through one large main which 
there branches to supply the various 
risers. One riser only is generally used 
for each tier of steam radiators. Fig. 45 
shows one- and two-pipe radiator con- 
nections. Frequently two-pipe connec- 
tions are made to a single riser pipe. 
When this is done a water type radi- 
ator must be used with the supply en- 
tering the top and the return leaving 
the bottom of the same side (See vapor 
heating systems). 

A third classification may be made, hav- 
ing reference to the manner of circu- 
lating the heating medium and to its pressure. This classifi- 
cation covers a multitude of inventions upon the attachment 
of which increased capacity and efficiency are claimed over 
the ordinary gravity systems. In outline, this classification 
may be stated as follows: 

Gravity Systems 

Steam systems, circulating steam at pressures 
greater than atmosphere. 

Water, open tank systems, circulating water by in- 
creased weight of water in return risers over 
warm water in supply risers. 




Fig. 45. 



Modified Gravity Systems 

Steam systems, circulating steam at atmospheric 
pressure or below. 



HOT WATER AND STEAM HEATING 125 

Water systems, circulating- water under pressure, 
at temperatures above those possible with the 
open tank systems and with accelerated veloc- 
ities. 

Combination steam and gas systems with radiators as 
heaters independent of a centralized heat supply. 

Systems mentioned in this classification are explained in 
Arts. 81 to 85. 

GRAVITY SYSTEMS. 

SI. .Steam and Hot Water Systems: — Ordinary low pres- 
sure steam installations operate at pressures from 1 to 10 
pounds gage. Relief valves are provided which release the 
steam when pressures tend to increase above the set maxi- 
inum and thus protect the boiler from excessive pressures. 
Pressures in the boiler are maximum. These decrease g^rad- 
ually along- the circuit of the supply and return mains be- 
cause of the frictional retardation of the circulating- steam, 
g-iving- a pressure drop between main and return near the 
boiler of % to 1 pound. The water in the return, therefore, 
stands above the water level in the boiler an amount suf- 
ficient to balance this differential pressure. All pipes in 
the system are g-raded for easy flow of the condensation 
back to the boiler. Each boiler must be fitted with a pres- 
sure gage, a safety valve or pop valve and a draft reg-ulat- 
ing device. Each radiator must have a first-class automatic 
air valve. 

An ordinary hot water installation has an open expansion 
tank at the highest point of the system to permit chang-e in 
volume in the water as it chang-es temperature, such systems 
operate at pressures equivalent only to the static head of 
the water in the system. Pressures at the boiler rarig-e from 
15 to 25 pounds gag-e for residence work. Water tempera- 
tures above 212°, therefore, will cause a loss of steam out 
the overflow of the expansion tank and are not considered 
advisable. Each boiler is fitted with a pressure g-ag-e or alti- 
tude gage to show the height of water in the expansion tank, 
a thermometer to show the temperature of the circulating 
water and a draft regulating device. Each radiator must 
have a compression air cock. 

82. Dia^ram.s for Gravity Steam and Hot "W^ater Piping 
Systems: — Figs. 46 to 51 inclusive show some of the methods 
of connecting up piping systems between the source of heat 
and the radiators. A, B, C and D show different methods 



126 



HEATING AND VENTILATION 



ONE PIPL STEAM SYSTEM -BASEMENT MAIN 




Fig-. 46. 



TWO PIPE STEAM SYSTEM-BASEMENT MAIN 




Fig-. 47- 



HOT WATER AND STEAM HEATING 



127 



« 




MILLS SYSTEM 




Wr 



STEAM -ATTIC MAIN 




M: 




}&t: 



Onv RETUFIK 



WET RETURN 



^ 



(),C^ DRY R-ETui 



C3CI3 
C3€3 



WETT RETufl^ 



Fig. 48. 



ONE PIPE! 'SYSTEM-HOT WATER 




Fig. 



128 



HEATING AND VENTILATION 



TWO PIPE SYSTEM HOT WATER -BASEMENT MAIN 




Fig-. 50. 



of connecting- between the radiators and mains. The 
branches below the floor and behind the radiators are for 
the purpose of taking up expansion. Short connections 
should be avoided. It will be noticed that the two-pipe 
steam systems have sealed returns ^vhere they enter the 
main return above the water line of the boiler. Dry returns 
frequently interfere with the circulation of the steam to the 
radiators by short-circuiting. Steam from the boiler follows 
the path of least resistance to each radiator and many times 
this path leads up the return line into the radiator instead 
of through the supply. In Fig. 47 suppose the radiators C 
and D increased in number to the right C, D', C", D", etc., 
and all connected to the main as shown and to the return 
without the loop. It is easy to see that steam from the 
supply main would flow through the radiators C and D into 
the dry return where it would continue to the 'end of the 
line and affect the easy flow of steam through the end radia- 
tors. If the main inlet to any radiator were restricted, the 
steam to that radiator would be supplied through its return 
branch thus blocking circulation and causing water-hammer. 
The only way to insure against this is to loater-seal each re- 
turn by connecting as shown or by connecting to a wet re- 
turn. 



HOT WATER AND STEAM HEATING 129 



f 1 






TO EXPANSION TA^ 



m6s= 



MILLS SYSTEM 



w© 



HOT WATER -ATTIC MAIM 






lOl 



^ ^^ 



:w 



o 



[ roup" Q 



PQ 




W^ 



:Ck 



Fig:. 51. 

Hot water gravity circulation is more easily retarded 
than steam circulation and g-reater care must be exercised in 
laying- out and installing the systems. Fig-. 50 shows the 
connections most frequently used with basement mains. 
Connections recommended for the Mills overhead hot water 
system are shown in Fig-. 51. Where all radiators in the 
same tier are connected flow and return to the same drop 
riser, circulation is frequently equalized in the radiators 
by O. S. Distributors turned ag-ainst the 
stream in the supply and with the 
stream in the return (See Fig-. 52). 

Basement radiation usuallj^ has poor 

circulation. In steam systems if the 

water of condensation is to be returned 

to the boiler it is placed on the ceiling- 

or wall as hig-h above the water line as 

possible. If the water is to be trapped 

Fig-. 52. to the sewer it may be placed on the 

floor. Hot water radiation may be placed at any elevation 

above (not below) the return inlet to the boiler. Circulation 

is improved, however, if the radiator supply is connected 




130 



HEATING AND VENTILATION 




Fig. 53. 

from some point above the basement. Fig. 53 sliows sucli 
connections. Increasing the drop increases the rate of cir- 
culation. 

MODIFIED GRAVITY SYSTEMS. 



S3. Atmospheric and Vapor Systems: — Low pressure 
steam systems 'are not as well adapted as hot water systems 
for moderate service, say on spring and fall days when only 
a small percentage of the full capacity of the heating system 
is required. Difficulty is experienced in keeping uniform 
temperature conditions in the radiators. In small plants, 
such as are found in residences where a constant attendant 
can not be provided, temperatures alternate rapidly between 
maximum and minimum. In an endeavor to meet the de- 
mand for a steam system which will serve for all outside 
weather conditions, a number of modified low-pressure 
steam systems, called vacuum, vacuo-vapor, vapor, modula- 
tion or atmospheric systems have been devised. It is claimed 
for these systems that they give better regulation and more 
uniform temperature conditions, also that they are free from 
air troubles. 

The term vacuum should properly not be applied to this 
class but should belong to those systems having a positive 
vacuum in the returns mechanically produced by action of 



HOT WATER AND STEAM HEATING 



131 




pumps, ejectors, etc., as explained in Chapter IX. There is 
one g-ravity system, however, that has some claiin to the 
name — the Mercury Seal Vacuum System. Fig-. 54 represents the 
outer coils of anj^ radiator. Inside the last coil 
is a mercury pot with a vertical iron tube con- 
nection for mercury column similar to the aver- 
ag-e barometer. The top of this tube is connected 
with the atmospheric side of the automatic air 
valve. When not in service the mercury in the 
column drops to the pot. When firing up, the air 
valve permits the escape of air but closes 
against steam. The mercury pot freely allows 
the escape of this air but does not permit its 
return. As a result the heating system (any 
kind of system) warms up and expels the air 
but when it cools down a partial vacuum is es- 
tablished and the water continues to boil at tem- 
peratures below 212°. If the system of piping 
and valves is very tight a partial vacuum may 
be maintained throughout the night, during 
which time steam will circulate at low pressure 
until the temperature falls say as low as 150°. 
Further it will heat up more quickly and with 
less fuel in the morning because of this partial 
vacuum. To have a mercury column at each radi- 
ator would be prohibitive because of the expense, 
consequently where this system is used the air 
lines are run to the basement in a similar 
way to those of the returns, collected together and attached 
to a mercury seal of sufficient size to expel the air from 
the entire heating system. Such a system is sometimes 
called an air-line system. The above arrangement is very de- 
sirable and is in sharp contrast to the ordinary system 
where the steam leaves the radiators as soon as the tem- 
perature falls below 212°. The practical difficulties in ob- 
taining and maintaining an air tight piping system, ho"wever, 
limits its use. 

The terms vapor, vacuo-vapor, modulation, atmospheric and 
the like are trade terms that are not especially distinctive 
but which indicate all the large number of gravity steam 
systems operating at pressures from — to 1 — pound gage. 
In these systems the radiators are water-type, two-pipe, 



Fig. 54. 



132 HEATING AND VENTILATION 

top connected and have packless valves and no air valves. 
Steam being lighter than air it first fills the top of the 
radiators and gradually forces the air downward and out 
the return to the atmosphere. The radiator outlet is usually 
on the opposite side of the radiator from the inlet, water of 
condensation and air both passing through this opening. 

The important feature in operating any gravity heating 
system at pressures near atmosphere and especially those 
having no automatic control on the air relief, is effective 
regulation. Where this is obtained there will be fairly uni- 
form temperature conditions within the radiator, sufficient 
heat emission to satisfy the room requirements, and no 
wastage of steam. Regulation may be applied at any of 
the four points in the system — at the boiler, in which case 
the drafts are controlled by a hydraulic head, a float locatec 
in a receiver at the end of the return main or by a pressure 
regulator connected to the steam space of the boiler — at the 
inlet valve to the radiator — at the radiator outlet — and at 
the atmospheric vent at the end of the return main. All 
systems of this kind have automatic draft regulation and all 
have radiator inlet valves that give more or less satisfac^ 
tory hand or thermostatic control. The essential differences 
in the various types, therefore, lie in the character of the 
regulation at the radiator outlets and at the air relief on the 
end of the return main. Classifying the many systems on 
the market, a few only of which w^ill be mentioned, they 
may be grouped under three general heads. 

Type 1, Fig. 55, has no positive regulation on the radia- 
tor outlets or on the air relief. (A thin water seal is here 
considered as no regulation since in every case a positive 
vent opening is provided for air). In estimating radiation 
for this type, 20 per cent, more is put in than would be re- 
quired for any low pressure steam system with closed re- 
turns. This extra radiation serves to condense the steam 
that may be admitted to the normal radiator beyond its re- 
quired condensing capacity. If too much steam is admitted 
for any given outside temperature it will pass into the re- 
turns and out into the air. In this system, therefore, it is very 
desirable that the best of regulation he applied to the draft dampers 
at the boiler ai>d also that careful adjustment be made on 
the valve inlets to the radiators. Since most vapor inlet 
valves are hg,nd operated and are subject to the eccentric- 
ities of the attendant, too much dependence should not be 



HOT WATER AND STEAM HEATING 



133 




Fig-. 55. 



Fig. 56. 



placed in this regulation. It will be noticed that the end of 
the main is separately vented and enters the dry return 
through a water seal. This serves to cut off direct steam 
circulation into the return. Two representative systems of 
this class are the Atmospheric and the Mouat-Squires. 

The damper regulator of the Mouat-Squires system is 
worthy of special mention. Fig. 56, tank A is filled with 
water to the overflowing point, the overflow connection be- 
ing opposite the fulcrum. Steam enters the regulator from 
the boiler through connection F, forces the water down in 
tank A and up through the flexible hose B and the hollow 
lever C into tank D, causing tank D to drop when a sufficient 
weight of water to overcome the weight of the counterbal- 
ance E has entered same. This causes the drafts to close. 
When the pressure decreases in the boiler, the water re- 
turns to tank A by gravity, causing the reverse operation of 
the regulator and dampers. The setting' of the' counter- 
weight E regulates the vapor pressure at which action 
takes place. 

A slightly modified form of- Type 1 (Broomell System 
Fig. 57) has a receiver at the end of the return main at the 
boiler and an air relief from the top of the receiver to the 
atmosphere. The air relief leads through a condenser to 
condense and return to the boiler any steam leaving- with 
the air. The end of the main may be separately vented or 
connected with the air relief. Fig. 58 show^s tw^o sections of 
the receiver. A copper float rides on the water in the re- 



134 



HEATING AND VENTILATION 



airrcueP^^ 




Fig. 57. 



Fig-. 58. 



ceiver and is connected by chain to the dampers. The level 
of the water in the receiver remains the same as that in the 
boiler as long as all the steam generated in the boiler is 
used in heating. When excess steam is generated the pres- 
sure increases, the water level rises in the receiver and the 
float closes the drafts. If the float rises high enough to lift 
the adjusting rod, it unseats a safety valve and blows off 
the steam. The reverse action takes place when the pres- 
sure drops. 




Fig. 59. 



Fig. 60. 



Type 2, Fig. 59, has no regulation on the radiator out- 
lets (radiators not shown) but has a condenser coil and 
thermostatic control on the air relief w^hich connects with 
both main and return. By the use of a check valve or mer- 
cury seal beyond the thermostatic valve a partial vacuum 
may be temporarily produced in the system. In this type 
thfe amount of radiation is normal and the steam pressure 
may rise above normal with automatic air release without 
waste of steam. The Moline Systpyn is typical of this class. 
Note the ejector, Fig. 60. This is supplied with steam from 
the end of the supply main and ejects the air and vapor 



HOT WATER AND STEAM HEATING 



135 



from the end of the return main into the condenser, from 
which the air is released through the air trap and the con- 
densation is returned to the boiler. 

Type 3, Fig-. 61, has a normal amount of radiation, a 
positive thermostatic control on the radiator outlets and an 
air relief connecting- with the ends of the main and return 
either mechanically or thermostatically controlled. Three 
representative systems of this class are the Dunham, Webster 
and IlJinois. Attention is called to the equalizer pipe be- 



TtlLRMO STATIC 
VALVE 



AIR VALVL- 



C 



UND or RETURN 



C 



LTURNMAir^ 



CNP OF ■STLAM MAIN 

PAMPER 
REGULATOR 



sSCALE POCKET-^ 




Fig. 61. 



tween the main and return at the boiler, the swing check 
between the return riser and the boiler and the scale pocket 
on the bottom of the return riser to protect the check from 
scale and dirt. Also notice the difference in levels bet"W^een 
the normal water line in the boiler and the lowest end of 
the return main. This requires a water column of at least 
27 inches to provide sufficient head to overcome the inertia 
of the check and to account for a small differential pressure 



136 



HEATING AND VENTILATION 




Fig. 62. 



between main and return. The air relief in this type as in 
the type preceding- may be made to close under pressure and 
pressures above normal may be used. Type 3 gives a more 
positive circulation in the mains and radiators, less danger 

of short circuits and greater 
pressure range than those sys- 
tems not equipped with ther- 
mostatic valves on radiator 
outlets. Steam pressure regu- 
lators, similar in action to Fig. 
62 are used for damper control. 
Atmospheric and vapor heat- 
ing systems that may at times 
be operating under pressures 
varying from 2 to 10 pounds 
gage are fitted with return 
traps that close the air re- 
lief when the differential pressure between main and re- 
turn reaches a fixed amount. At the same time live steam 
is "automatically admitted to the top of the* trap forcing the 
collected return water through the check into the boiler. 
The air vent remains closed and action continues as an ordi- 
nary closed steam system until the differential pressure falls 

to normal when the action is 
reversed and it again becomes 
an open relief atmospheric sys- 
tem. The Webster return trap 
(Fig. 63) shows one of the sim- 
plest forms of these traps. 

84. 3Iodified Open Tank Hot 
AVater Systems: — A number of 
modifications have been adapted 
^^S- 63. ^Q iQ^r pressure hot water heat- 

ing systems for the purpose of increasing the tempera- 
tures, pressures and velocities of the circulating water above 
those obtained by the open tank system. Out of a large 
number of systems four of these will be mentioned as type 
representatives. Increasing temperatures permits a reduc- 
tion in radiation so as to compare with that of steam sys- 
tems. This is desirable since large radiators are an obstruc- 
tion in any room. With increased velocities pipe and fitting 
sizes may be reduced. This also is very desirable in any 




HOT WATER AND STEAM HEATING 



137 



system from the standpoint of adaptability. In addition any 
reduction of this kind causes a reduction in first cost. 

In the Honeywell System (Fig-. 64) a purely American sys- 
tem, a mercury seal tube is connected between the upper 
point of the main riser and the expansion tank. This is de- 
^ signed to hold a pressure within the system at 

< that point of about 10 pounds gage. Water 

from the system fills the casement and presses 
down upon the top of the mercury in the bowl. 
Increasing the pressure in the system lowers 
the level of the mercury in the bowl and forces 
the mercury up the central tube A until the 
differential pressure is neutralized by the static 
head of the mercury. If the pressure becomes 
great enough to drop the level of the mercury 
to the tube entrance, water and steam will 
force through the mercury to chamber D and 
from thence through the expansion tank to the 
over-flow. Any mercury forced out of tube A by 
the velocity of the water and steam, strikes 
deflecting plate C and drops back through an- 
nular opening B to the mercury bulb below. 
As the pressure is reduced in the system the 
mercury drops in tube A to the level of that in 
the bulb and water from the expansion tank 
passes down through the mercury seal into 
the heating system to replace any that has 
out of the expansion tank. This action is 
automatic and is controlled entirely by the pressure within 
the system. The only loss, if any, is that amount of water 
which goes out the over-flow. A similar arrangement is 
used in the Cripps System. In this the mercury seal is placed 
beyond the expansion tank and puts the expansion tank 
under pressure. 

The extra pressure made possible by the Honeywell or 
Cripps apparatus makes it possible to carry the circulating 
water at temperatures as high as 240°, which is above that 
of the average low pressure steam system. With tempera- 
tures as high as this there is undoubtedly an increased dif- 
ferential temperature between flow and return which would 
tend to increase the velocity of the water and make It pos- 
sible to reduce pipe sizes. 




Fig. 64. 
been forced 



138 



HEATING AND VENTILATION 



The Koerting System (Fig-. 65), invented by German engi- 
neers, is an open tank system with a series of motor pipes 
leading from the upper part of the heater to a mixer, where 
the steam which has been formed in the heater and motor 
pipes is condensed by part of the circulating- water entering 
through the by-pass from the return. The velocity of the 
steam and water through the motor pipes and the partial 
vacuum caused by the condensation in the mixer produces an 
acceleration up the flow pipe. 



'=31 





Fig. 



Fig. 66. 



The BrucJcner System (Fig. 66), invented by an Austrian 
engineer, is an open tank system with two expansion tanks. 
Heater E delivers the hot water (above 212°) up the flow 
pipe to receiver R, where a separation takes place between 
the steam particles and the water, thus causing an accelera- 
tion up the motor pipe to expansion tank A. The -water in 
flow pipe 2 has a temperature slightly below that in 1. After 
passing through the radiators the water in 3 is at a lower 
temperature than that in 2. The steam particles which have 
collected in expansion tank A above the water line are con- 
densed in V. The acceleration in the system is thus pro- 
duced by a combination of the upward movement of the 



HOT WATER AND STEAM HEATING 



139 



steam particles in motor pipe 1 and the induced upward cur- 
rent in 2 toward condenser "F. It will be noticed by compar- 
ing with Fig". 65 that the condensation in one system takes 
place before the expansion tank and in the other system 
after it has passed the expansion tank. Each of the systems 
illustrated may be carried under pressure by applying a 
safety valve as at B, a mercury column as in Fig. 64, or by 
an expansion tank located high enough to give sufficient 
static head. 

The Reck System, invented by a Danish engineer, is illus- 
trated by Figs. 67 and 68. Water passes from the heater 



fr\ 





Fig. 67. 



DETAIL OF A, B.AND C 

Fig. 68. 



up the main riser to condenser C and thence into expansion 
tank A as a supply to the flow pipes of the system. Steam 
from a separate boiler is admitted to mixer B above the con- 
denser and enters the circulating water just below the ex- 
pansion tank. The velocity of the steam and the partial 
vacuum caused by the condensation induces a current up the 
flow pipe to the expansion tank. When the water level in 
the expansion tank reaches the top of the overflow pipe the 
water returns to the steam boiler through condenser C where 



140 



HEATING AND VENTILATION 



it gives off heat to the upper current of the circulating 
water. It will be seen that the circulating water in the 
system and the steam from the boiler unite from the inlet 
at the mixer to the expansion tank. On all other parts of 
the systems they are independent. 

Fig. 69 is a modification of this same principle, wherein 
air is injected in the riser pipe at B and causes acceleration 
by a combination of the partial vacuum produced by the 
steam condensation as just men- 
tioned and the upward current of 
the air particles as in an air lift. 
Steam enters through pipe J and 
ejector H to the mixer at B where it 
is condensed. In passing through H 
air is drawn from tank E and enters 
the main riser with the steam. The 
upward movement of this air 
through the motor pipe to the tank 
induces an upward flow of the water 
in the main riser. By this combina- 
tion there are formed three complete 
circuits, water, steam and air, unit- 
ing as one circuit from the mixer B 
to expansion tank E. The steam 
furnished in principle 3 may be sup- 
^^S- 69. plied by a separate steam boiler or 

by steam coils in the fire box of a hot water boiler. 

Acceleration is also produced by some piece of mechan- 
ism as a pump or motor placed directly in the circuit. This 
principle is discussed under District Heating and will be 
omitted here. 




85. Gas- and Electric-Steam Heating Systems; — A gas- 
steam system of heating, similar in many respects to the 
Rector gas radiator system (Art. 74), is frequently used. In 
this case the heating unit is a combination gas stove- and 
steam radiator. The gas supply (either natural or artificial) 
is automatically controlled by a diaphragm valve from the 
pressure within the radiator. Radiators without exhaust 
pipes may be used with artificial gas for limited heating, but 
they should be supplied with exhaust pipes in every case 
where natural gas is used and where artificial gas is used in 
amounts to render the room air impure. An electric-steam 



HOT WATER AND STEAM HEATING 



141 



system is sometimes used for the same service. The radia- 
tors are made of pressed steel, electrically welded and sealed. 
The radiator contains a small amount of distilled water (a 
6-section type having- about a quart which never needs re- 
placing-). The electric heating unit is about the same capac- 
ity as th.ose used in electric flat irons. The heating unit, 
partially surrounded by water and under partial vacuum, 
heats readily. Systems of this type are in use in climates 
where only moderate heating is necessary. 

80. Piping Connections: — Many heating systems have 



I 



(1) 

TEE BRANCH 




BRANCHES IN 
SAME PLANE 



(2) 



DOUBLE ELL 
BRANCH 




(5) ^^ 

Y BRANCH 




eti= 



(^) DRAINAG-E ON 
STRAIGHT RUN 
REDUCTION IN PIPE 



(6) 



DRAINAGE AT CORNER 
REDUCTION IN PIPE 




BOXING MAIN 
AROUND BEAM 



Fig. 70. 



142 



HEATING AND VENTILATION 



been crippled by improper piping- connections. Figs. 70 and 
71 show some of tlie standard forms. In this connection a 
few suggestions may be valuable. (1) A steam main may 
branch right and left through a straight tee providing the 
lineal expansion of the branches is provided for. (2) Right 




MAIN. BRANCH 

TO RISER 
PERPENDICULAR AND 
PARALLEL TO WALL 




MAIN BRANCH 
TO RISER 
DOUBLE PITCH ELLS 




DIRT POCKET 

BOTTOM OF RISER 

REMOVABLE CAP 




f 0. S. FITTING 
ON RISER TO 
UPPER RADIATOR 




CI I) ^ 

©VmAIN BRANCH 
TO RISER 45° 
AND DOUBLE PITCH ELL 





MAIN RETURN BRANCH 
DOUBLE PITCH ELL 



Fig. 71. 
and left branches through straight tees in hot water sys- 
tems should never be used. A double sweep ell should be 
used instead, this will divide the two streams of water with- 
out causing eddy currents. (3) Any branch that is to be 
favored should be taken from the top of the main by vertical 



HOT WATER AND STEAM HEATING 143 

or 45° lines. No hot water branches should ever be taken 
off the side of the main. (4) Offset branches provide ex- 
pansion facilities. (5) Hot water mains may branch through 
y fitting's. This is ideal for circulation but does not absorb 
expansion as readily as 90° turns. (6, 7) Steam mains which 
change size should be graded on the bottom for satisfactory 
drainage. This may be done at a corner by a reducing ell 
pitched slightly downward or on a straight run by an eccen- 
tric fitting. (8) Steam mains may pass an obstruction by 
boxing around the obstruction, the drop providing drainage 
and the rise the steam circuit. (9) Mains are kept ly^ to 3 
feet from the wall, well supported from the ceiling and free 
to move in any direction to allow for expansion. The cor- 
ners of the main should not be anchored by running diagon- 
ally to the riser. Branches should be run perpendicular to 
and parallel with the wall. (10, 11, 12) Double-pitch ells 
should lead to risers in all places where necessary. Long 
branches to risers are to be avoided where possible. (13) 
Dirt pockets should be provided at the bottom of return 
risers where there is danger of clogging valves, (14, 15, 
16) Radiation on the upper floors will rob the lower floor 
radiation, consequently retarding influences such as O. S. 
fittings, reducers and offsets should be put in to give advan- 
tage to lower floors. (17) Radiators should be connected 
with branches sufficiently long to take up expansion. (18) 
Water pockets should be avoided in horizontal mains and 
branches. All pipes should be well pitched for drainage. (19) 
Risers may be run within the wall or in closed chases in the 
face of the wall for appearances. Complete encasement 
within the wall, however, should be made only with the 
knowledge and consent of the owner since in many cases 
walls have been ruined by defective pipes. (20) Branches 
may also be run within the floor construction, but extra care 
should be used in the laying. 



CHAPTER VII. 



HOT WATER AND STEAM HEATING 



BOILERS, RADIATORS, FITTINGS AND APPLIANCES. 

87. Steam Boilers and Water Heaters: — Heaters for 
supplying- hot water and boilers for supplying- steam to 
heating systems may be divided into three classes: round 
vertical, having capacities of 250 to 1500 sq. ft.; sectional, 
having capacities of 300 to 9000 sq. ft. ; and water tube or fire 
tube, having capacities of 10000 to 40000 square feet of direct 
steam radia;tion. Round and Sectional boilers (Figs. 72 and 
73) are made of cast iron, are of the portable type and need 
no special casings other than the plastic coverings to reduce 
radiation. Fire tube and water tube boilers (Figs. 74 and 
75) are of wrought iron or steel and are encased in brick 
work. Boilers of the largest capacities are water tube type 
and are always used in central station work. Heating boil- 
ers for residence work are usually of the sectional type. These 
boilers are very flexible and may be increased in capacity by 
adding sections to existing boilers to meet increased require- 
ments. In some installations it is better to install two 
boilers of somewhat reduced capacity (say % of the calcu- 
lated capacity) and either boiler will more nearly meet the 
average load. This is frequently done where break downs 
may cause serious inconvenience. In general it may be said 
that products of the various manufacturers show but little 
difference in design between hot water heaters and steam 
boilers and as a result the two types are usually referred to 
as boilers. 

Boiler capacity depends principally upon the amount and 
arrangement of the grate and heating surfaces. Grate sur- 
face is the gross area of the fuel bed at the top of the grate. 
Heating surface refers to those boiler plates that have the 
fire or heated gases on one side and water on the other. 
Heating surfaces are of two kinds, direct and indirect (some- 
times called prime and secondary). Direct surfaces are those 
so located as to receive the direct heat or radiant ray of 



HOT WATER AND STEAM HEATING 145 




146 



HEATING AND VENTILATION 



m 



the fire. Indirect surfaces are all those not included under 
direct, i. e., those that are in contact only with the heated 
gases of combustion. Direct surfaces transmit more heat 
per unit of time than the same area of indirect surface be- 
cause of the greater difference in temperature between the 
two sides of the plate. For this reason boilers have as much 
direct surface as is possible to give them. The average 
amount of heat transmitted through boiler plates will vary 
from 1600 to 2500 B. t. u., for heating boilers and 2000 to 
3000 B. t. u., for power boilers. The rate of heat transmission 
for clean metal surfaces should be practically the same for 
either direct or indirect locations. See also Art. 61 on fur- 
nafee heating surfaces. 

Proper combustion of the fuel and the most efficient 
transmission of the heat of the fire across the plates to the 
water are of prime importance. It is easy to see therefore 



mm/M 




Fig. 76. 
that the one feature of boiler design under continual study 
is the construction of the fire box or furnace. This is 
especially true of the boilers burning bituminous or soft 
coals. The average hand fired furnace, cared for by the 
average fireman is a nuisance in any business or residence 
district because of the smoke. In large plants the mechan- 
ical stoker which fires slowly and continuously at the front 
of the fire has proved the best remedy but in small plants 
where hand firing is necessary and where the fire is charged 
three to four times each twenty-four hours the problem is 
more difficult. A number of smokeless furnaces, represented 
by Fig. 76, have been developed along the lines of the 



HOT WATER AND STEAM HEATING 



147 



Hawley down draft furnace with water tube grates above 
the fire and fire grates below. Fuel is fed into the space 
above the water tubes (coking- chamber) and there loses 
the volatile matter and hydrocarbon g-ases. These g^ases 
are practically all consumed in passing- over the lower fire 
and throug-h the leng-th of the combustion chamber. The 
lower g-rate catches the coke product from the upper g-rate 
and is occasionally replenished by a charge of fresh coal 
near the front of the fire. These furnaces produce prac- 
tically smokeless combustion and are being- increaslng-ly 
used. 

The latest design of soft coal furnace is that shown in Fig-. 
77. This is of the sectional down-draft, grateless type and 




Fig. 77. 



is especially designed for bituminous and soft coals, having 
a magazine above the fire which serves the purpose of sup- 
ply box and coking chamber. In this arrangement com- 
bustion takes place as in the Hawley furnace, the liberated 
hydrocarbons being consumed while passing through the 
entire length of the combustion chamber to the chimney. 



148 HEATING AND VENTILATION 

Round and sectional types of boilers have ratios of 
g-rate surface to heating surface varying between 1 to 15 
and 1 to 25, and water tube or fire tube boilers varying be- 
tween 1 to 40 and 1 to 60. The arrangeinent of the heating 
surface differs very much, each manufactured product hav- 
ing a distinctive design. According to Prof. Kent "for com- 
mercial and constructive reasons, it is not convenient to 
establish a fixed ratio of heating surface to grate surface 
for all sizes of boilers. The grate surface is limited by the 
available area in which it may be placed, but on a given 
grate more heating- surface may be piled in one form of 
boiler than in another, and in boilers of one general form 
one boiler may be built higher than another, thus obtaining 
a greater amount of heating surface. The rate of burning 
coal and the ratio of heating to grate surface both being 
variable, the coal burning rate and the ratio may be so re- 
lated to each other as to establish a rate of evaporation of 
2 lbs. of water from and at 212° per sq. ft. of heating sur- 
face per hour." 

Boilers may he selected by grate surface, heating surface, 
coal burned per hour, pounds of steam evaporated per hour 
and heating capacity in square feet of radiation (including 
mains). Manufacturers' catalogs give boiler ratings in 
terms of radiation supplied, with grate surface, heating 
surface and installation sizes for units of different capac- 
ities. The best method of selecting- a heating boiler is to 
estiinate the required grate surface of the boiler that will 
theoretically supply the given radiation and check this 
amount with the catalog data (See Art. 100). Considerable 
care must be exercised in the selection of the type of boiler 
to fit any given set of conditions. To illustrate: the grate 
and fire box should be designed favorable to the burning of 
the kind of coal that would be generally used; the boiler 
selected should permit of easy cleaning especially if it is a 
soft coal burner; the arrangement of the heating surfaces 
should be such that there will not be an excessive friction 
as the gases pass through the boiler; with an inside chim- 
ney there is little danger of lack of draft and any form of 
down draft boiler may be used, while with an outside chim- 
ney of ordinary construction there may be a question as to 
the use of such boilers; also, the kind of attention and the 
frequency of firing must be taken into account. For fur- 
ther study of boiler types and operations see Marks' M. E. 



HOT WATER AND STEAM HEATING 



149 



Handbook, Kent's M. E. Pocket-Book, Gebhardt's Steam 
Power Plant Engineering-, Hirshfield and Barnhard's Ele- 
ments of Heat Power Engineering, and trade catalogs. 

Combination heaters, are frequently installed to supply both 
warm air and steam or warm air and warm water to the 
same plant. For such systems a combination heater as 
shown in Fig. 26, Art. 65, is needed. It consists essentially 
of a warm air furnace with a steam or water radiator in 
the upper part of the fire pot. The radiator through the 
connected piping supplies heat to those sections of the build- 
ing where satisfactory air circulation could not be had. The 
principal difficulty encountered in these combined systems 
is in obtaining the proper proportion of the heating surface 
of the furnace to that of the radiator to suit varying de- 
mands upon the system. 

88. Boiler Accessories: — Water heaters are equipped 
with pressure gages or mercury columns for registering the 
pressures carried within the system, thermometers on the 
supply and return mains to give the differential tempera- 




Fig. 78. 




Fig. 79. 



ture of the circulating water, and automatic draft apparatus 
controlled by thermo-regulation from the temperatures of 
the supply water or by a thermostat from the temperature 
of the room air. Steam boilers are supplied with pressure 
gages as in water heaters, safety valves or pop valves to 
relieve any excessive pressures, water glass and gage cocks 
to register the water levels, and automatic draft apparatus 
controlled by a diaphragm valve from the pressure of the 
steam in the supply main, by a float from the water level in 
the return main or by a thermostat from the temperature of 
the room air. Fig. 78 is a thermo-regulator for water 
systems. It operates from the elongation and contraction 
of a sylphon bellows enclosed within a cast iron casing. 



150 HEATING AND VENTILATION 

The bellows, a brass, accordion pleated cylinder, is closed at 
both ends and contains a volatile fluid -which vaporizes at 
low temperatures and causes varying" pressure within the 
bellows. Water from the boiler circulates between the bel- 
lows and the casement and as the temperature of the water 
changes the state of the volatile liquid its pressure changes 
and the bellows increases or decreases in length and oper- 
ates the draft. A modiflcation of this type of regulator is 
used on steam system. In this the regulation is by steam 
pressure from the inside of the sylphon bellows (see Fig. 62). 

Fig". 79 shows a diaphragm regulator which Is usually 
attached to the steam space of the boiler or to the steam 
main close to the boiler. For details of specialties including 
glass gages, gage cocks, etc., see American Radiator and 
United States Radiator company's catalogs. For care of 
boilers and furnishings see Art. 115. 

89. Radiators, Classification as to Material: — Radiators 
may be classified according to the materials used in their 
production as cast iron, pressed steel and pipe coil. "Wall 
thicknesses of cast radiators are ^ to ^^ inch. Pressed 
radiators are formed from sheet steel plates. Each section is 
composed of two pressed sheets that are welded tog^ether by 
a double seam around the edge and riveted between the col- 
umns. The sections of cast radiators are connected by mild 
steel or malleable push or screw nipples which serve as pas- 
sageways between the sections for the heating medium. 
The malleable nipple is subject to occasional hidden defects 
from the process of casting but is not subject to corrosion 
as is true of the steel nipple, hence it is usually preferred. 
Pressed steel sections are welded together. Cast iron radia- 
tors have the disadvantage of ^sveight and bulk and have a 
comparatively large internal volume, averaging a pint and 
a half per square foot of surface, but they are practically 
free from corrosion. Each radiator after being- assembled 
is tested to 100 lbs. per sq. in. gage pressure. Pressed radia- 
tors have an internal volume approximating one pint per 
square foot of surface. 

Radiators composed of pipes in various forms (vertical 
or horizontal) are commonly referred to as coils. They are 
not much used for direct or direct-indirect work because of 
the unsightliness. They are frequently used in indirect and 
plenum systems and are generally used in the direct heating 
of shops, factories and greenhouses. In coil heaters 1-inch 



HOT WATER AND STEAM HEATING 151 

pipe is the standard size, however, in some cases (green- 
houses) coils are used as large as 2 inches in diameter. 
Standard 1-inch pipe is rated at one square foot of heating 
surface per three lineal feet and has about one pint of 
containing capacity per square foot of heating surface. 

90. Classification as to Form: — Radiators may be classi- 
fied according to form as one, two, three and four column 
floor types, xoall type and flue type. These terms refer only to 
cast and pressed radiators. The column of a radiator is one 
of the unit fluid-containing elements of which a section is 
composed. When a section has only one vertical unit it is 
called a single column or one column radiator, when it has 
more than one it is a two column, three column or four 
column type. End sections are called leg sections, inter- 
mediate ones are loop sections. The legs on all pressed steel 
radiators are detachable. A wall radiator is a one-column 
type, so designed as to be of the least practicable thickness. 
It frequently presents the appearance of a heavy grating 
and is designed to have 5, 7 or 9 square feet of surface, ac- 
cording to the size of the section. One column floor radia- 
tors made without feet are often used as wall radiators. 
A flue radiator is a very broad type of the one column radia- 
tor, the parts being so designed that the air entering be- 
tween the sections from below is compelled to travel to the 
top of the sections before leaving the radiator. This type 
is well adapted to direct-indirect work. 

There are many special shapes of assembled radiators 
such as stavrway radiators built up of successive heights of 
sections to fit along the triangular shaped wall space under 
stairways, pantry radiators built up of sections to form a tier 
of heated shelves, dining room radiators with an oven-like 
arrangement built in between sections, and vnndoio radiators 
built with low - sections in the middle and higher ones at 
either end to fit neatly around a low window. Fig. 80 shows 
a number of these common forms used in practice. Pigs. 
81, 135-137, show methods of building up pipe coil heaters. 

91. Classification as to Heating- Medium: — A third classi- 
fication according to the heating medium employed, gives 
rise to the terms steam radiator and hot water radiator. Cas- 
ually one w^ould notice little difference between the tw^o, but 
in construction there is a vital difference. A steam radiator 
has its sections joined by nipples along the bottom only, 
but a hot water radiator has both top and bottom connec- 



152 



HEATING AND VENTILATION 




Stairway Type Dining Room Type Flue Type Circular Type 



CAST RADIATORS 







Two-Column 
Type 



Three-Column 
Type 



Four-Column 
Type 



PRESSED RADIATORS 




m 

M 

* i 



Single-Column Two-Column Three-Column 

Type Type Type 



Wall Type 



Fig. 80. 



HOT WATER AND STEAM HEATING 



153 



tions. This is quite essential to the proper circulation of the 
water. Steam type radiators are always tapped for pipe 
connections at the bottom. Hot water radiators may have 
the supply connections at the top and the return connections 
at the bottom, or both connections at the bottom. Hot water 
radiators can be heated very successfully with steam, but 
steam radiators cannot be used for hot water. Vapor sys- 
tems are supplied with two-pipe, hot water type radiators. 
Radiators must have at least tioo tappings, one below for 
the entry and exit of the heating: medium, and one on the 
end section opposite (near mid-height for steam and at the 
^ i p.^ top for hot water) for air 

discharge as shown by Figs. 
46 and 48. They may have 
three tappings, a supply, a 
return and an air tapping as 
shown in Figs. 47, 49, 50 and 
51 (For fittings see Figs. 
88-92). 

92. Effect of Height and 
Width of Radiator Upon 
the Transmission of Heat: 
— In selecting a radiator 
height for a given place the 
governing feature is usu- 
ally the floor space allowed 
for the radiator. Thus, if 
a radiator 26 inches high 
requires so many sections 
that it is too long for the 
space allowed, a 32-inch or 
a 38-inch section may have 
to be taken. High radiators are less efficient than low radia- 
tors because as the air is heated in passing up the outside of 
the sections the differential temperature between the inside 
and the outside becomes less, and less heat is transmitted per 
unit area. By the same reasoning, horizontal pipes (coils) are 
more efficient than any other form of heating surface. 
Also, wide radiators are less efficient- than narrow radiators 
because of higher air temperatures between the coils. 




Fig. 



154 



HEATING AND VENTILATION 



Rates of heat transmission obtained by tests for cast 
iron radiators and pipe coils are: (Steam 215°, room air 70°). 



Cast Radiators 


1-Col. 


2-Col. 


3-Col. 


4-Col 


20 


inches high 


1.93 


1.85 


1.75 


1.64 


23 




1.89 


1.80 


1.70 


1.59 


26 




1.86 


1.76 


1.66 


1.56 


32 




1.79 


1.69 


1.59 


1.49 


38 




1.74 


1.65 


1.55 


1.45 


45 






1.60 


1.50 


1.40 



Cast Wall Coils 

Heating- surface 5 sq. ft., long side vertical 1.92 

Heating surface 5 sq. ft., long side horizontal 2.11 

Heating surface 7 sq. ft., long side vertical 1.70 

Heating surface 7 sq. ft., long side horizontal 1.92 

Heating surface 9 sq. ft., long side vertical 1.77 

Heating surface 9 sq. ft., long side horizontal 1.98 

Pipe Coils 

Single horizontal pipe 2.65 

Single vertical pipe 2.55 

Pipe coil 4 pipes high 2.48 

Pipe coil 6 pipes high 2.30 

Pipe coil 9 pipes high 2.12 



93. Effect of Condition of Radiator Surface on the 
Transmission of Heat: — The efficiency of a radiator is af- 
fected by the condition of its outer surface. Painting, bronz- 
ing, shellacing or covering the radiator surface in any man- 
ner affects the rate of transmission of heat. A series of 
tests conducted by Prof. Allen at the University of Michigan, 
indicated that the ordinary bronzes of copper, zinc or alum- 
inum caused a reduction in the efficiency below that of the 
ordinary rough surface of the radiator of 20 per cent., while 
white zinc paint, terra cotta enamel and white enamel gave 
the greatest efficiency, being slightly above that of the 
original surface. Numerous coats of paint, even as high as 
twelve, seemed to affect the efficiency in no appreciable 
manner, it being the last or outer coat that always deter- 
mined at what rate the radiator would transmit its heat. 
Reference. — Trans. A. S. H, & Y. E. The Effect of Painting- 
Radiator Surfaces, J. R. Allen, Vol. XV, p. 229. 



HOT WATER AND STEAM HEATING 



155 



94. Effect of Housing on the Heat Transmission of 
Radiators: — Experiments were conducted by Prof. K. Brab- 
bee of the Royal Technical Institute of Berlin, to determine 
a relation between the efficiencies of exposed and enclosed 
radiators. The results of these tests were reported in the 
Heating- and Ventilating- Magazine, May, 1914, and the fol- 
lowing is a brief summary. No records were kept of vol- 
umes and temperatures of the air, these differing so greatly 
that the observations were of little value. The radiators 
used were two and three column, plain surface, ten sections, 
three inch centers. The two column radiators were 8.5 
inches wide and the three column radiators -were 9 inches 
wide. 

Tests were first run w^ith the radiators set in the ordi- 
nary way (2.5 inches from the wall, not enclosed and in 




what is ordinarily called still air) giving results for K as 
follows: 49 in. 2 col. = 1.62; 24 in. 2 col. = 1.74; 50 in. 3 
col. = 1.38; 26 in. 3 col. = 1.5. These values were then used 
as a basis of comparison for showing increased or reduced 
efficiencies of various housings. At the conclusion of the 
first series, tests were conducted upon the same radiators 
housed as shown in Fig. 82. 



156 HEATING AND VENTILATION 



RESULTS FOUND. 



A. The best spacing- was found to he r = f = 2.5 inches, 
although K was about 8 per cent, less than in normal setting 
when thus enclosed. should be at least the width and 
length of the radiator. When O was less than this amount ; 
A' rapidly decreased. For open inlets c = length of radiator 
and d min. = 4 inches. In such cases K was reduced 15 per 
cent. With inlet screened 7t was much less. 

B. With )• = f — 2.5 inches, the housing without top 
increased A' as much as 12 per cent, because of the increased 
velocity of the air over the radiator due to the chimney action. 
The^ best results were obtained when the area of the inlet 
in square inches was approximately ten times the heating 
surface of the radiator in square feet. K increased by mak- 
ing- enclosvire higher than radiator. 

C. Narrow shelves placed 3 inches or more above the 
radiators had little effect. Where a was such as to be flush 
with the front of the radiator and ^ = 3 inches K fell off 
about 5 per cent. On low radiators the loss was about 10 
per cent. In either high or low radiators where t = i to 5 
inches, A' was about normal. Curved deflectors under shelves 
showed little or no gain in efficiency over the square corner. 

D. Make r =z 2.5 inches and / = 3 to 6 inches. Where 
* = 3 inches K was reduced 8 per cent. Where t = Q inches, 
A' was approximately normal. Side spacing had little or no 
effect. 

E. A very inefficient form of housing even with d and 
open slots. Under the very best conditions K was reduced 
25 to 35 per cent. 

F. With r =z f = t = 2.5 inches. A' was reduced about 20 
per cent. 

G. A very inefficient form of housing. K was reduced 
30 to 40 per cent. 

Tests of hot water radiators under the same conditions 
of housing verified the values found for steam. A convenient 
toay to apply the ahove is to figure the square feet of radiator 
surface for normal setting and then multiply this amount by 
the following approximate values: A, 1.10; B, 1.00; C, 1.07; 
D, 1.10; E, 1.30; F, 1.20; G, 1.40. 

In places where direct-indirect radiation is desired and 
no provision has been made for it in the building plan. Fig. 
83 is suggested as a good substitute. The housing around 



HOT WATER AND STEAM HEATING 



157 



the radiator accelerates the draft and the damper arrange- 
ments give opportunity for all outside air, mixed outside and 
inside or all inside air at the discretion of the occupants. 

95. Amount of surface in Radiat- 
ors: — Table XIII gives according to 
the columns and heights, the num- 
ber of square feet of radiation sur- 
face per section in cast and pressed 
radiators. This table presents ap- 
proximate values in very compact 
form from extended tables in the 
manufacturers' catalogs. An approx- 
imate rule supplementing this table 
and giving, to a very fair degree of 
accuracy, the square feet of surface 
in any standard radiator section, is 
as follows: muUiply the height of the 
sections in inches hy the number of col- 
umns and divide by the constant 20; the 
result is the square feet of radiating sur- 
face per section. The rule applies 
with least accuracy to one column 
radiators. 

96. Pipe Fittings: — Common and 
special. — Pipes of standard diameters 
and random lengths are made from 

both wrought iron and steel. These pipes are cut, threaded 
with standard threads and connected with standard malleable 
or cast iron fittings to form any desired combination. Wrought 
iron pipe is considered by some to be more durable than 
steel pipe for general service but because of less first cost 
steel is more frequently employed. For exact diameters, 
surfaces, etc., see Table 29, Appendix. 

Lengths of pipe are connected in straight runs by unions 
and couplings. Unions are threaded right-hand, and right- 
and-left. As distinguished from the right union the right- 
and-left has one end tapped right hand and the other 
left hand and connects between sections of a straight 
run already laid. Flanged couplings (usually packed 
between the flanges) are generally employed in con- 
necting large sized pipes, and in addition are used on 
any sized pipe in places where sections may need fre- 




Fig 



158 



HEATING AND VENTILATION 



TABLE XIII. 



Dimensions and heating- surfaces of radiators, per section. 



Type of 
radiator 





w 






o 




-a g 


"n 


csM 




^.s 


fn.S 


^ o 


"^fl 


§1 




^s 



Square feet of surface for over-all heights 



45" 



32" 26" 23" 22" 20" 18" 17" 16" 14' 



1 Col. O. I 

2 Col. O. I 

3 Col. O. I 

4 Col. C. O.... 

Mue wide 

Flue narrow _. 
1 Col. press 

3 Col. press 

4 Col. press 



51/2 

81/2 

10 

111/4 

121/2 

81/2 

51/4 

8% 
12 



10 



2y4 



1% 



3% 



4% 



11/2 



4% 



Wall rad. 
C. L _... 
Thick. 3" 



A. R. f 13i4"x29i/8"] 9 13i4"x22" 1 7 

\ [ sq. 1- sq. 

U. S. [ 14i/8"x29i4"J ft. 14i/8^'x22%"J ft. 



13Wxl6%"l 5 

l-sq. 

14y8"xl6y2"J ft. 



quent removal for repairs or inspection. Elbows (usually 
called ells) change the direction of any run throug-h 90". 
See double pitch ells, Art 86. Tees are used where branches 
leave a straight run at 90°. They are sometimes made with 
a 45° instead of a 90° branch and are called laterals or Y 
fittings. Couplings, elbows, tees and laterals are made with 
varying inlet sizes. These are called reducing couplings, re- 
ducing ells, reducing tees, etc., and are specified as follows: 
state the sizes of the straight run, large and small, and 
second state the size of the branch. For illustration, a 
2" X 1%" X 1" reducing tee will change the size of the straight 
run from 2" to 1%" and give a branch of 1". Where branches 
are made for water heating they should be so formed as to 
give a free and easy movement to the water. In such cases 



HOT WATER AND STEAM HEATING 



159 



it is desirable to use pipe bends having- a radius of three to 
five pipe diameters, instead of the common elbow. In all 
cases pipe ends should be carefully reamed before assem- 
bling- to remove the burr left by the cutter. This is most 
important in water heating- as the burr on small pipes is 
sometimes heavy enough to reduce the area of the pipe by 
one-half, thus creating- serious eddy currents and increasing 
the friction. 





Fig. 84. 



Eccentric reducing fittings (Fig. 84) are often of value in 
avoiding water pockets in steam lines. These should always 
be used on horizontal steam mains (Fig-. 70) when reduc- 
tions are made from one size to another. Bushings should not 
be used as reducing fittings for water lines because of the 
restriction to flow due to the square end of the bushing. 

Valves are of two general types, glote and gate. Globe 
valves are installed on steam lines but they should not be 
used on horizontal steam mains where the seat -will cause a 
water pocket and hinder drainage. Gate valves offer an un- 
obstructed passage for both 
steam and water. They are 
recommended on all water 
lines and are being increas- 
ingly used on steam lines. 
Globe valves, however, are 
less expensive and are more 
easily repaired. The best 
type of globe valve has a 
renewable composition seat. 
Fig. 85 shows sections of 
each type. 

Those used 





Fig. 85. 
Radiator inlet valves are usually angle type 



on the ordinary low pressure steam systems are packed with 
soft packing and those used on systems which are occasion- 



160 



HEATING AND VENTILATION 



ally under partial vacuum are necessarily of the packless type. 
Those used on atmospheric and vacuum systems generally 
have graduated control. Fig-. 86 shows several models of 
these valves. Water radiator valves are of the quick opening 
or butterfly type, opening and closing with a quarter turn of 
the handle and having a small hole through the valve to 
permit just enough leakage when closed to keep the radia- 
tor from freezing-. Far radiator return valves to he used on 
mechanical vacuum systems, See Chapter IX. 




HOT WATER AND STEAM HEATING 



Ifil 



Check valves are of two kinds, siving and lift. They are not 
needed on the ordinary low pressure gravity water or steam 
systems, but where used swing checks should be specified 
rather than lift checks, for the former operate at less differ- 
ential pressure and offer much less resistance to the passage 
of water and steam. Fig. 87 shows a section of each. 





Fig. 87. 
Air valves serve a most important function in heating 
systems. Air is constantly accumulating in the radiator 
and its frequent or automatic removal becomes necessary 
if all the radiating surfaces are to remain effective. For 
this purpose small hand operated valves or compression 
cocks, Fig. 88, are inserted near the top of the end section 
in all hot water radiators, and automatic valves are inserted 
at one-balf to two-thirds the height of the last section on 




Fig. 88. 
steam radiators. Air valves are not essential to two-pipe 
steam systems and are sometimes omitted. They are not 
needed on vapor systems and are always omitted. Fig. 89 
shows a common type of automatic 
air valve using the principle of the 
expansion stem. As long as air is in 
contact with the stem it remains con- 
tracted and the needle valve is open 
for air release. When steam enters 
Fig. 89. the valve it surrounds the stem and 

expands it sufficiently to close the needle valve and 
prevent steam loss. Fig. 90 operates on the principle 
of the evaporation of a volatile liquid in a closed 
container. The composition of this liquid is such that 




162 



HEATING AND VENTILATION 



it evaporates at the steam temperature and causes a 
deflection of the base of the container sufficiently to move 
the valve pin and close the valve. Air temperatures being 
less than steam temperatures, the reverse action takes place 
when air collects around the stem and the valve opens for 
air release. Water jetting-, which is frequently found with 
air valves, is eliminated by the floatation of the container 
which is free to lift and ride the water that collects in the 
float chamber. A modification of this valve (Fig. 91) has, 
in addition to the thermal features just mentioned, an at- 
mospheric air pressure feature which permits its use on 
vacuum systems. As the pressure is reduced in the radia- 
tor, atmospheric air presses upward against diaphragm 1 
and forces the pin valve against its seat. It will be seen 
that when the pfessure within the radiator is less than 
atmospheric the differential pressure closes the valve and 
keeps air out. When the pressure within the radiator is 





Fig-. 90. Fig. 

slightly above atmospheric the valve stands open except at 
the times when all the air is exhausted and the steam holds 
the valve closed through the expansion member. By the 
combined action of both expansion members air may be re- 
leased continuously but it can not reenter. Valves operat- 
ing- on either the thermal or differential pressure principle 



HOT WATER AND STEAM HEATING 



163 



or both may be had for quick venting- oh mains, coils and 
other parts of a heating- system. Fig-s. 92 and 93 operate on 
the principle of the difference of expansion between two dis- 
similar metals. In the first one the expansion member is 
made of two strips of dissimilar metals brazed tog-ether in 
the form of a loop. These metals expand at different rates 
under chang-es of heat and cause endwise movement of the 





Fig-. 92. 



Fig. 93. 



valve rod, thus opening- or closing- the valve. The hollow 
float serves the purpose of catching- any sudden surg-e of 
water and avoids flooding-. The second one employs a long- 
central tube which carries at the top, the valve seat of the 
needle valve. The needle itself is carried by the two side 
rods. As long- as the air flows up throug-h the central pipe, 
the needle valve will remain open, but when steam enters 
the tube it expands and carries the valve seat upward 
ag-ainst the needle, thus closing- the valve. The size and 
streng-th of parts make this form a very reliable one. For air 
line valves to be used on mechanical air line systems, see Chapter IX. 
97. Expajision Tank: — The expansion tank is a neces- 
sity in all atmospheric hot water systems. Its function is 
to serve as a supply tank for the system and also as a take- 
up for the excess volume due to the heating- of the water. 
Fig-. 94 shows a typical cylindrical g-alvanized tank supplied 
In capacities of 8, 10. 15, 20, 26, 32, 42, 66, 82 and 100 g-allons; 
the averag-e size, 16 in. diam. x 30 in. hig-h is rated for 
approximately 1000 square feet of radiation including- mains. 



164 



HEATING AND VENTILATION 



Fig-. 95 is an £lut(?hiatic, self-filling-, coppei* lined tank ap- 
proximately 20 in. X 9 in. X 10 in. and is supplied for sys-,, 
terns up to 2000 square feet capacity. The g-alvanized tank! 
is tapped 1-inch for the overflow and expansion pipes, andi 
the automatic tank is tapped %-inch supply, 1^4 -inch ex- 
pansion and 11/2 -inch overflow. The expansion tank is ol 

TO 

VENTILATING 
FLUE 



kCOLD 
\ WATER 

LEVEL 




TD riEAREST RETURMjJ [J TO MEAREST FLOW 

Fig-. 94 Fig. 95. 

located in the bath room or a closet near the bath room an( 
its overflow connected to the proper drainage. It shouh 
be set at least two feet above the highest radiator. Th( 
connection between this tank and the heating- system i£ 
often by a branch from the nearest radiator riser. The best ' 
connection is by an independent riser from the basement 
return main. The capacity of the tank for any system up 
to 1500 square feet may be obtained by the approximate 
rule: divide the total radiation ty JfO to obtain the capacity of 
the tank in gallons. 

98. Fire Coils or AVater Backs for Hot AVater Supply: — 
Pipe coils or cast iron water chambers (water backs) may be 
installed in the combustion chamber of any furnace, hot 
water or steam plant for heating- the domestic hot water 
supply. Care must be exercised in installing- these fixtures 
to see that there is an up-flow for the water from the point 
of entering to the point of leaving the fire box. Soft water 
should be used in these icatei' systems wherever possible because of 
the lime and other deposits throxon off from the hard water. If it 
becomes necessary to circulate hard water the coils should 
be examined at least once each year to see that they are not 
filled with lime. Lime deposits cut down the heat transmis- 
sion, cause the pipes to burn and endanger the plant in 
making- it more liable to explosion. In many plants the 
heating- surface on these coils is excessive. On cold days 
under heavy fire the water in the tank is maintained at the 



HOT WATER AND STEAM HEATING 165 

boiling point when lower temperatures would be more satis- 
factory. This condition may be corrected by attaching- water 
connections to the circulating pipes outside the fire box and 
running these leads to a hot water radiator where heat is 
most needed. Each lead to the radiator and the flow pipe to 
the hot water tank should be valved with gate valves so as 
to regulate the circulation in each line. 

99. Corrosion of Pipes: — Much has been said and writ- 
ten about the internal wastage or wearing away of steel 
and wrought iron pipes conveying hot water, but owing to 
the fact that such a long time is necessary for a compara- 
tive test and surrounding conditions are so changeable, no 
authoritative data have yet been found to prove conclu- 
sively to pipe users that either of the two (steel or iron) is 
longer lived than the other. Most of the pipe now used in 
the country is of mild steel, probably because of the fact 
that this pipe can be manufactured and marketed at a lower 
price. Nevertheless if it may be shown by any conclusive 
proof that wrought iron pipe is more durable the price 
would be a secondary feature in the purchase. One of the 
most convincing papers on this subject yet presented to the 
engineering profession is found in the Trans. A. S. H. <& Y. E., 
Vol. 24, p. 217, by F. N. Spellor and R. G. Knowland. A copy 
of the paper is also found in Technical Paper 236, Depart- 
ment of the Interior, Bureau of Mines. 



CHAPTER VIII. 



HOT WATER AND STEAM HEATING. 



PRINCIPLES OF THE DESIGN, WITH APPLICATION. 
100. Selecting Boilers for Capacity: — To determine the 
necessary boiler capacity for a given installation, find the 
theoretical grate surface to supply the calculated heat loss 
plus 20 to 30 per cent, to cover that lost from the mains and 
risers, and select a boiler having- at least this amount of 
grate from the catalog data representing the type of boiler, 
desired. Current practice adds 25 to 50 per cent, to the 
theoretical grate as a safety margin. Rule. — To find the the- 
oretical grate surface in square feet, divide the total B. t. u. required 
per hour for maximum heating service ty the product of the pounds 
of coal estimated per square foot of grate surface per hour {rate of 
combustion), the efficiency of the furnace and the heat value of the 
fuel in B. t. u. per pound. (See Equation 46). 

The following rates of combustion may be used for in- 
ternally fired heating boilers: 





4-6 


6-10 


10^18 


18-30 






Lbs. coal per sq. ft. grate per hour 


5 


6 


8 


10 



Boilers with constant attendance, such as power boilers, 
may have a higher rate of combustion. 

Catalog ratings are usually obtained from test data 
taken when the boilers are burning anthracite coal. Where 
boilers are to be used w^ith soft coals the 50 per cent, addi- 
tional capacity mentioned above had best be taken because 
of the larger volume needed per pound of coal and because 
of the sooty nature of the coals. 

Application. — Assume a total building heat loss (includ- 
ing mains and risers) of 150000 B. t. u. per hour; soft coal 
13000 B. t. u. per lb.; 5 pounds coal per sq. ft. of grate per 
hour; and boiler efficiency 60 per cent.; then from Equation 



HOT WATER AND STEAM HEATING 167 

46, G. A. = 550 sq. in. Add 50 per cent. = 825 sq. in. = 5.7 
sq. ft. From the Ideal Fitter this gives an S-25-5. Sectional 
boiler with a hard coal rating of 1100 sq. ft. of heating sur- 
face. 

101. Calculation of Radiator Surface — Direct Radiation: 
— In designing a hot water or steam system, the first impor- 
tant item to be determined is the square feet of radiation to 
be installed in each room. Nearly all other items, such as 
pipe sizes, grate area, boiler size, etc., are estimated with 
relation to the radiation supplied. The correct determina- 
tion then, of the square feet of radiation in these systems 
is all important. The general equation used to obtain the 
square feet of radiation for any room is: 

total B. t. u. lost from the room per hour 



R 



K (av. temp. diff. between inside and outside of rad.) 



Rule. — To find the square feet of radiation for any room divide 
the calculated heat loss in B, t. u. per hour by the quantity K times 
the difference in average temperatures between the inside and outside 
of the radiator. 

Expressed in symbols 

H (orH') 
Rw = (49) 



/ ta + tu t + to\ 

H (or H') 



H (or H') 
Rs = • (50) 



Where Rw and Rs = sq. ft. radiation required for water 
and steam heating, ta and tb = water temperatures entering 
and leaving radiators, t and to = temperatures of air passing 
over radiator and t.i — temperature of the steam. In ordi- 
nary direct radiation calculations the term [(# + ^o) -=- 2] is 
usually taken 70. 

In Art. 92, the rate of transmission K, (Amount of heat 
transmitted through one square foot of surface per hour per 
degree difference in temperature between the inside and the 
outside of the radiator) obtained from tests, varies inversely 
with both the height and the width of the radiator, being as 
high as 1.93 for low 1-column and as low as 1.40 for high 



168 HEATING AND VENTILATION 

4-column radiators. For extreme accuracy these values may 
be used. For ordinary service, however, they may be sum- 
marized Vi^ith fair accuracy into: 

low radiators — 16 to 23 inches — 1.8 
medium " — 23 to 32 " — 1.7 
high " — 32 to 45 " — 1.6 

All applications in this hook will he taken 1.7. 

"With hot water as the heating- medium the temperatures 
within the radiator for the open tank system are about as 
follows: entering- the radiator 180°; leaving- the radiator 
160°; average temperature on the water side 170°. To find 
the amount of hot water radiation for any other average 
temperature of the water, substitute the desired average 
temperature in the place of 170. The maximum drop in tem- 
perature as the water passes through the heater will seldom 
be more than 20 degrees even under severe conditions. The 
temperature of the entering water may be assumed as high as 
212° if it is considered necessary in which case each square 
foot of surface becomes more efficient and the total radia- 
tion in the room may be reduced. Since radiators become 
less efficient from continued use, it is best to design a sys- 
tem w^ith lower temperatures as stated and under stress of 
conditions the capacity may be increased by raising the 
flow temperature to the boiling- point. With a room tem- 
perature of 70°, a 26-inch 2-col. or 3-col. hot water radiator 
will g-ive off 1.7 X (170-70) = 170 B. t. u. per square foot 
per hour and the amount of radiation is: 

For hot water, open tank direct radiation as usually applied 
W FT 

Rw = = = .006 fl- (51) 

1.7 (170 — 70) 170 

For the Honeywell system and others maintaining pressures 
above atmospheric, use higher water temperatures in the 
general equation. For example, suppose these temperatures 
are entering at 220° and leaving 200°, we have 

TT JJ 

Bw = rr = .0042 17 (52) 

- --- 238 



(220 + 200 \ 

— I '") 



A steam system may be installed to work at any pres- 
sure from a partial vacuum of, .3ay 10 pounds absolute, to as 



HOT WATER AND STEAM HEATING 169 

high a pressure as 75 pounds absolute. To calculate the 
proper radiation for any of these conditions use Equation 50 
and substitute the proper steam temperature. 

The temperature within a steam radiator carrying steam 
at pressures varying between and 3 pounds gage may be 
taken 220°; then the total transmission for this radiator will 
be 1.7 X (220 — 70) = 255 B. t. u. per square foot per hour, 
and the amount of radiation 

For Steam, gravity direct radiation as usually applied is 

Rs — = , safe value = = .004 H (53) 

1.7 (220 — 70) 255 250 

It will be seen from Equations 51 and 53 that Rw = 1.5 jK.?. 

This ratio is frequently used 1.6. (See also Art. 137 for 

logarithmic equation). 

For atmosiyheric and vapor systems with individual traps on 

the return end of each radiator 

Rx = = , safe value = = .00417 H (54) 

1.7 (212 — 70) 241 240 

For atmospheric and vapor systems with open return and 20 

per cent, excess radiation for cooling surface 

5 X 1.2 H 

Ry = = = .005^- (55) 

1.7 (212 — 70) 200 

Note. — Equations 51 to 55 will meet average conditions. 
If for high radiators, low radiators, wall or pipe coils it is 
considered necessary to be more specific, use the values K 
given in Art. 92. 

Application. — Referring to the standard room with H = 
15267, Art. 39, the equations quoted above give: 

(51) hot water, open tank 91 sq. ft. 

(52) hot water, closed tank 64 sq. ft. 

(53) Steam, to 3 lbs. 61 sq. ft. 

(54) Steam, vapor, closed returns 64 sq. ft. 

(55) Steam, vapor, open returns 76 sq. ft. 
Assuming a 26-inch 3-col. type cast radiator, we have as 

follows: 

for (51), 24 sections, radiator 60 inches long. 

for (52), (53), (54), 17 sections, radiator 42.5 inches long. 

for (55), 21 sections, radiator 52.5 inches long. 

Many empirical equations and rules have been devised 
(based, somewhat upon the rational Equations 49-55) in an 
attempt to simplify calculation, but their applications are 



G 

— + 
2 


W 

10 


■ + 


c 

60 ~ 


24 + 19.2 + 


31.6 = 


74.8 sq. t 


+ 


20 


+ 


C 
100 ~ 


48 + 9.6 + 


19 = 7 


6.6 sq. ft. 


3 (/ 

4 


+ 


TT 

10 




H 

100 


^ 36 + 19. 


2 + 19 


= 74.2 sq 


— + 


W 

10 


+ 


(7 
200 


24 + 19.2 + 9.5 = 


52.7 sq. 1 


2 




w 


C 


2 







170 HEATING AND VENTILATION 

untrustworthy unless used with that discretion which comes 
with years of practical experience. The reason why such 
empirical rules often g:;ve erroneous results is because of 
the fact that nothing- is said concerning exposure and equiv- 
alent wall, such as floors and ceilings. Some of these equa- 
tions and their applications to the "Study" Art. 62, where 
G = 48, TF = 192 and C = 1900 are: 

(a) /?, 

(b) E 

(c) Ru- = h — + — = 36 + 19.2 + 19 = 74.2 sq. ft. 

(d) Us = 

(e) Rs = — ((? + \ ) = — (48 + 9.6 + 19) = 

3 20 100 3 

51 sq. ft. 

G W C 

(f) Rs = \ \ = 24 + 9.6 + 9.5 = 43.1 sq. ft. 

2 20 200 

Checking these Equations 51 and 53 we have Ru- = 76 sq. ft. 
and Rs = 52 sq. ft. 

102. Direct-Indirect Radiation: — This system of heating 
is used in some homes and in many moderate sized school 
buildings. It has the simplicity of direct radiation with cer- 
tain ventilating possibilities which may be had at a reason- 
able first cost. In discussing direct-indirect heating, how- 
ever, it should be remembered that the ventilating feature 
of the system is very erratic, having a tendency to move too 
much air when the wind pressure is against that side of the 
building where the radiator is located and too little air 
when the direction of air movement is reversed. The re- 
quir ment of a constant supply of 1800 cubic feet of air per 
person can not be maintained by convection processes solely. 
The reason for this is the low velocity of the air entering- 
the building (even in some cases a reversal of movement) at 
times when the air pressure is reversed. In order to keep 
from over heating the room with too much direct-indirect 
radiation (found necessary in keeping up the air supply) 
some reduction must be made from the usual requirement of 



HOT WATER AND STEAM HEATING 171 

ventilation when clesig-ning- this type of system, say to 1200 
or 1500 cubic feet. Direct-indirect radiation should always be used 
i7i connection with inner loall ventilating stacks and preferably those 
fitted with aspirating coils. Such stacks have a pull on the 
room air and overcome to a certain extent the back draft of 
the room air over the radiator. 

In school house heating", direct-indirect radiation is 
usually installed in connection with direct radiation. The 
two kinds may be assembled in each radiator or certain 
radiators may be all direct and others all direct-indirect as 
preferred. Ten to twelve sections of the standard radiator 
are usually connected to one wall box. Wall boxes are made 
in varying sizes; one standard form being sold in three sizes 
— 8x24, 8x30 and 8x36 inches, having approximately 100, 125 
and 160 square inches net area respectively. High radiators 
should be used because of the chimney effect in overcoming back 
drafts. Loxo pressure hot water, vacuum or atmospheric steam sys- 
tems should be used with caution because of the danger of freezing. 

In estimating direct-indirect radiation with the accom- 
panying duct sizes, it may be done by either one of two 
methods: first, estimate the direct-indirect radiation to supply 
the necessarj'- heat to warm the amount of ventilating air 
desired and add sufficient direct radiation to make up the 
balance of heat for the calculated heat loss, H; second, esti- 
mate the direct radiation necessary to supply H and add 50 
per cent, for indirect heat given to the entering air, then 
enclose and connect to wall boxes the necessary radiation 
for direct-indirect work. 

Application. — Assume a standard recitation room in a 
school building having 13" brick walls; the room to be 24 
ft. X 30 ft. one side and one end exposed, window area = one- 
sixth the floor area, 12 ft. ceiling, // = 50000 B. t. u., and 
arrangement of seating (excepting 8 feet across the front 
of the room reserved for instructional purposes) 15 square 
feet of floor space per pupil. 

Analysis. — Number of pupils 35. Amount of air required 
for ventilation (say 1400 cu. ft. per pupil) = 49000 cu. ft. 
per hour. Select medium sized wall box 125 sq. in. net wind 
area. With favorable conditions we may expect 1 to 2 cu. ft. 
air per min. per sq. in. net wall box area (air velocity 2.5 to 
5 f. p. s.) Call this 1.5 cu. ft. We have 125 X 1.5 X 60 = 
11250 cu. ft. per hour per wall box. 11250 -i- 1400 = 8 pupils 



172 HEATING AND VENTILATION 

supplied. Pour wall boxes 8 in. x 30 in. will approximately 
supply all the pupils at the rate of 1400 cu. ft. per person. 
These theoretically should give 11250 x 4 =: 45000 cu. ft. 
air per hour. Since this number of radiators makes a good 
division for the room, the same number of radiators may be ' 
used. In the direct-indirect arrangement just mentioned, 
with average air velocities, air temperatures may be raised: 
from zero to 125° and each sq. ft. of included radiation will 
give off approximately 375 B. t. u, per hour (when the out-, 
door air is below zero it will be advisable to recirculate part 
or all of the air). . The heat given to the air will be [45000 X 
(125 — 0)] ^ 55 = 102272 B. t. u. and the radiation will be 
102272 -^ 375 = 273 sq. ft. = four radiators 68 sq. ft. each 
(approximately 160 cu. ft. of air per sq. ft. of radiator sur- 
face). In all probability these would be taken 12 sec. 38-in. 

3 col. 60 sq. ft. With 60 sq. ft. in each radiator the total 
heat given off to the air in the room will be approximately 

4 X 60 X 375 = 90000 B. t. u. Of this amount of heat 56 
per cent. (50404 B. t. u.) is used to raise the temperature of 
the air from zero to 70° and 44 per cent. (39600 B. t. u.) is 
used to raise it from 70° to 125°. This latter amount will be 
given off to the room air and is a credit to the heat loss H. 
50000 — 39600 = 10400 B. t. u. to be supplied by direct radia- 
tion. 10400 H- 250 = 41.6 sq. ft. = 8.3 sections, 38-in. 3-col. 
radiation. Assuming this to be 8 sections and divided 
equally among the radiators we have four 38-in. 3-col. radi- 
ators each consisting of 12 sec. direct-indirect and 2 sections 
direct radiation. This would be considered a fairly satisfac- 
tory arrangement. The direct-indirect radiation should be 
installed so as to operate as such on outside air or as direct 
on recirculated air if desired. 

Under the second method suggested find 50000 ~ 250 = 
200 sq. ft. of direct radiation to offset H. Add 50 per cent. = 
300 sq. ft. total = four 38-in. 3-col. radiators each 15 sec. 
divided 12 sec. direct-indirect and 3 sec. direct. 

Comparing the amount of radiation obtained by the first method 
toith the amount required if heated by direct radiation, we have 

direct radiation .... 200 sq. ft. = 1.00 

direct-indirect radiation - 240 sq. ft. = 1.20' 

Combined 

direct radiation - - 40 sq.ft. = .20 



{ 



HOT WATER AND STEAM HEATING 



173 



103. Gravity Indirect Radiation: — This provides one of 
the most satisfactory systems of heating-. In all essentials 
it compares with the furnace system, with the furnace re- 
placed by individual steam 
or hot water radiators. 
(See Fig-. 96). It is an im- 
provement over the direct- 
indirect system in that 
there is a fairly constant 
air movement to the room. 
Radiators of either the ex- 
tended pin or ribbed type 
are used. Some of the 
standard sizes a-j e g-iven in 
Table XIV. 

The indirect radiator 
should be set 20 to 24 
inches above the water line 
of the boiler. There should 
be a clearance of 10 inches 
at the top and 8 inches at 
the bottom between the casing- and the radiator, for cold air 
and warm air chambers, but the casing- on the sides and ends 
should be close to the radiator. The radiators are suspended 
from the joists and connected to the steam and return mains 
in such a way as to permit free expansion and contraction. 
All pipes must be g-raded for free drainag-e to the boiler. 

TABLE XIV. 




Fig. 96. 









Per- 








Sanitary 


fec- 






Gold Pin 


School 
Pin 


tion 
Pin 


Pin Indirect 


Sq. ft. H. S 




















per sec. 


12 


15 


20 


15 


20 


10 


10 


15 


20 


L 


36 


36 


.36 


36% 


361/8 


361/4 


36V4 


36% 


36 


H 


9 


111/2 


151/4 


111/2 


15% 


9H 


8% 


11% 


143^ 


C 


3V4 


»y4 


ay* 


4 


4 


- 2% 


3 


3 


31/2 



Pipe sizes may be the same as those used on any two-pipe 
radiator having- equivalent condensation. Low radiator sec- 
tions (h = 6 to 10 inches) are recommended for residences 
and offices. Hig-h radiators (h = 10 to 15 inches) are recom- 
mended for schools. 



174 HF'^ATING AND VENTILATION 

To determine the atnount of air circuUUed per hour, read 
Arts. 49-51. In residences and offices, air as a heat carrier 
will be sufficient. In schools and auditoriums there will be 
an excess of air for ventilation. Where this is true the tem- 
perature of the air leaving the radiator should be corre- 
spondingly below what it would be if only heating- were con- 
sidered. (See Art. 52). 

The lowest temperature of the entcriny air may be taken zero. 
At lower temperatures part or all of the air should be recir- 
culated. The temperature of the air leaving the radiator depends 
upon the velocity of movement over the radiator. 

Table XV, from experiments by J. R. Allen, cols. 2 and 3, 
gives air temperature rise in passing over the radiator. 
TABLE XV. 



!1 











B. t. u. transmitted 


Cubic f oe.t 


Risft in 


Pounds of steam 


per sq. ft. of 


of air 


temperature 


Condensed per sq. ft. 


radiation per degree 


passing- 
por sq. ft. 


of the air 


of radiation 


difference in temp. 








between steam and air 


of radia- 














tion 


Stand- 


Long 


Standard 


Long 


Standard 


Long 


per hour 


ard pin 


pin 


pm 


pin 


pin 


pin 


m 


147 


140 


0.125 


0.150 


0.80 


0.95 


7^) 


143 


137 


0.170 


0.210 


1.17 


1.27 


1(10 


140 


135 


0.240 


0.260 


1..51 


1.60 


12.5 


LS8 


132 


0.295 


0.310 


1.85 


1.90 


m) 


135 


12!) 


0.3.55 


0.300 


2.22 


2.20 


175 


1.32 


120 


0.410 


0.405 


2.. 57 


2.47 


2(M) 


130 


123 


0.470 


0.4.50 


2.90 


2.72 


22.') 


127 


120 


0.530 


0.490 


3.25 


3.00 


250 


123 


118 


0.585 


0.530 


3.00 


3.20 


275 


121 


115 


0.645 


0.570 


3.90 


3.40 


30O 


119 


112 


0.700 


0.610 


4.22 


3.60 



In the design of indirect heating systems there are cer- 
tain ajjproximate values which may be recommended as rep- 
resenting fairly standard practice. These values which fol- 
low may be used in connection with Table XV. 
Cu. ft. of air per sq. ft. of radiation 

(residence) steam 150 water 100 

K for residence heating- 2.2 

Cu. ft. of air per sq. ft. of radiation 

(schools) " 200 " 133 

K for school heating 2.6 

Temperature of air entering radiator zero 

Temperature of air leaving radiator 

(residence) 100, 125 and 150 



HOT WATER AND STEAM HEATING 175 

Sq. ft. of radiation determined by Equation 56 or 57 

H' 
Rs = (56) 



^('■-— -) 



H' 



^•(-i^-^) 



(57) 



Where terms are as stated in Art. 101. 

Sq. in. of flue area per sq. ft. of rad. Steam Water 

Height between c. of rad. and c. of reg. 5 ft. 2.00 1.33 

10 ft. 1.40 .90 

20 ft. 1.00 .66 

Select type of radiator from catalog data. 

Indirect radiators are usually arranged to permit recir- 
culation of the air from the house when desired. For other 
information on recirculating ducts, registers, etc., see fur- 
nace heating. 

Application 1. — In Art. 62, the Living Room (// = 15267) 
and Chamber 1 (H = 10583) are to be supplied with indirect 
steam heat, design the heaters and heat lines. 

Solution. — Assume t„ = O; t = 125 and ts = 220; then for 

the Living Room 

55 X 15267 

Q (Eq. 33) - = 15267 

125 — 70 

15267 X (70 — 0) 

//' (Eq. 30) = 15267 -\ = 34698 

55 

34698 
Rs (Eq. 56) = = 100 sq. ft. 



/ 125 + \ 



Efficiency of radiator = 2.2 (220 — 62.5) = 346.5 B. t. u 

Amount of circulating air = 100 X 150 = 15000 cu. ft. 

Compare this with calculated value of Q. 

Check amount of indirect radiation with direct radiation, 
Art. 101, Eq. 53. This shows an increase of (100 — 61) -^ 
61 = 64 per cent, above the calculated direct radiation for 
the same room. 



176 HEATING AND VENTILATION 

Square inches warm air duct area = 2 X 100 = 200. 

Square inches cold air duct area = 200 x .8 = 160. 

For Chamber 1, with temperatures as before 

55 X 10583 

Q = • = 10583 

125 — 70 

10583 X (70 — 0) 

//' = 10583 H = 24143 

55 

24143 

Rs = = 70 sq. ft. 

125+0 \ 
220— I 



i 

1 



'■'i 



2 / 

Efficiency of radiation = 346.5 B. t. u. 

Check amount of circulating- air. 70 X 150 = 10500 cu. ft. 

Compare this with Q. 

Check indirect radiation with direct radiation, 66 per 
cent, increase. 

Square inches of warm air duct area =r 1.25 X 70 = 88 : ! 

Square inches of cold air duct area = 88 X .8 = 70 . • 

Application 2. — In Art. 102, a school room 24 x 30 ft. has {i 
a heat loss of 50000 B. t. u. and has 35 pupils. It is required I 
that this room be heated by indirect radiation, design the l 
heaters and heat lines. ) 

Solution. — Q = 35 X 1800 = 63000; to = 0; ts = 227. j 

50000 X 55 

+ 70 = 113.6 say 114°. 



63000 

H' =50000 + 63000 X 1.27 = 130180. 

130180 

Rs = = 295 sq. ft. 

114+0 \ 



!.6 I 22: 



2 / 

Efficiency of radiator = 442 B. t. u. 

Check amount of circulating air, 63000 -=- 295 = 213 cu. ft. 
per sq. ft. radiation. 

Check amount of indirect radiation with direct radiation for the 
same room and find direct = 200, indirect = 295 ; approximately i 
1.00 : 1.50. 

104. Asijiratiiig Coils: — For the most efficient service, 
direct-indirect and indirect heating should be accompanied 
by a positiiw withdrawal of the air from the rooms through - 
ventilating ducts. This is true especially in the heating of 
school buildings. Individual electric driven fans may be 



1 



HOT WATER AND STEAM HEATING 



177 



housed in the vent ducts or the vents may be g-athered to- 
gether in the attic and housed in around one exhaust fan, 
but these plans require extra care in installing' and are ex- 
pensive in first cost. Furthermore, in many places electric 
power can not be had. In such places indirect radiation 
(aspirating coils) may be placed in the vents as shown by 
Fig. 97 and the heat given off will produce convection air 
currents which insure a positive 
withdrawal of the room air. This 
is not an efficient method of pro- 
ducing draft, in fact any other 
workable method should be em- 
ployed where possible. 

In installing aspirating- coils 
they should each be piped direct 
from the boiler room. The valves 
should be located in the boiler 
room and should be under the 
control of the boiler attendant. 
When the rooms are not occupied, 
steam should be cut out of the 
coils and the vent dampers closed 
to avoid depleting the room of 
warm air. When coils are cut off 
they should be drained to avoid 
freezing. 
The amount of radiation to install in each vent flue 
varies in different localities. Fairly satisfactory results 
seem to be obtained with two vents to each room (25 x 30 x 
12 ft.) and 30 to 40 square feet of cast iron indirect radiation 
in each vent. For sizes of vent ducts above heaters see cor- 
responding sizes in furnace heating. 

105. Greenhouse Heating: — In estimating greenhouse 
radiation the problems are essentially different from those in 
ordinary house radiation. In greenhouses glass surface is 
large, wall surface is small and air circulation is compara- 
tively less. The rational equation for heat loss, therefore, 
has less to do with volume and except in unusual cases may 
be considered to have but two terms — glass and vi^all. Where 
volume is accounted for, calculate H as in Chap. III. Instead 
of ordinary cast iron radiation, the radiating surfaces are 
wrought iron or steel pipes 1^/4-, 1%- or 2-inch diameter (or 




Fig. 97. 



178 



HEATING AND VENTILATION 



cast pipes 2 ^/^ - to 4-inch diameter) assembled as coils with 
manifold headers. The values of K for these coils may be 
found in Art. 92. Although test values run as high as 2.65 
for single horizontal pipes it is a safe plan because of the 
dirt deposits on and in the pipes, to allow an average value 
of not to exceed 2.2 for all wrought iron or steel coils and 
1.8 for all cast iron coils. Find // by Equation 26 (or 27), 
using only glass and wall equivalent and substitute in Equa- 
tions 49 and 50. For all practical purposes H =. {G -\- .25 
Eq. W) 70. 

Assuming wrought or steel coils and zero weather 

H 

Rro — = .0045 H 



2.2 (170 
H 



70) 



lis 



.0030 H 



(58) 



(59) 



2.2 (220 — 70) 
If the desired indoor temperature is other than 70' 



this 

temperature should be substituted for 70 in the equation. 
Assuming t' = 70 we have Rw = .32 (G + .25 Eq. W) and 
Rs = .21 (G + .25 Eq. W); = one square foot of H. W. radiation 
to 3.1 square feet of equivalent glass area and one square foot of 
steam radiation to Jf.8 square feet of equivalent glass area. 
Table XVI (Model Boiler Manual) shows the amount of sur- 
face for different interior temperatures and different tem- 
peratures of the heating medium. 



TABLE XVI. 





Temperature of water in heating pipes 


Steam 


Temp, of 
air in 






140° 1 160° 1 180° [ 200° 


Three lbs. pressure 


Green- 
house 


' 




Square feet of glass and its equivalen 


t proportioned to one 




square foot of surface in heating 


pipes or radiator 


40° 


4.33 


5.25 


6.66 


7.69 


8.0 


10.00 


4.5° 


3.63 


4.65 


5.. 55 


6.66 


7.5 


8.50 


.50° 


3.07 


3.92 


4.76 


5.71 


7.0 


7.40 


.55° 


2.63 


3.39 


4.16 


5.00 


6.5 


6.60 


60° 


2.19 


2.89 


3.63 


4. .33 


6.0 


5.90 


65° 


1.86 


2.53 


3.22 


3.84 


5.5 


5.20 


70° 


1.58 


2.19 


2.81 


3.44 


5.0 


4.80 


75" 


1.37 


1.92 


2.50 


3.07 


4.5 


4.30 


80'° 


1.16 


1.63 


2.17 


2.73 


4.0 


3.90 


85° 


.99 


1.42 


1.92 


2.46 


3.5 


3.50 



This table is computed for zero weather; for lower tem- 
peratures add IV2 per cent, for each degree below zero. The 



HOT WATER AND STEAM HEATING 



179 



last column was calculated from Equation 50 (K = 2.2) and 
added for purpose of comparison. 

Empirical riiJes for greenhouse radiation are sometimes 
g-iven in terms of the number of square feet of g'lass surface 
heated by one lineal foot of 1 14 -inch pipe. One such rule is 
— "one foot of 1^-inch pipe to every 2^/4 square feet of g-lass, 
for steam; and one foot of 1 14 -inch pipe to every 1% square 
feet of glass, for hot water, when the interior of the house 
is 70° in zero weather." Great care should be exercised in 
rating and selecting the boilers and heaters. It is well to 
remember that the severe service demanded by a sudden 
change in the weather is much more difficult to meet in 
greenhouses than in ordinary structures, and that a liberal 
reserve in boiler capacity is highly desirable. 

Both steam and hot water systems are in general use. 
Where continuous heat may be obtained throughout the 
night from a central plant a steam system is very desirable. 
In the isolated plant where the steam pressure drops during 
the night time a hot water system will give more satisfac- 
tory service in cold weather because it guarantees a better 
circulation of heat throughout the night. 

The same rules apply in running the mains and risers as 
apply in the ordinary hot water and steam systems. In 
greenhouse work the head of water in a water system is 
necessarily very low and tends to make the circulation 
sluggish, but with sufficient pipe area to reduce the friction 
a hot water open tank system having a very low head may 
be made to work satisfactorily. In some houses the coils 
are run along the wall below the glass and supported on 
wall brackets; in others they are run underneath the 
benches and supported from the benches with hangers. In 
greenhouses with very large exposure there are sometimes 
required both wall and bench coils, also, a certain amount in 




Fig-. 98. 



180 HEATING AND VENTILATION 

the center, 6 to 7 feet from the floor. In all of these piping' 
layouts it is necessary that as much rise and fall be given 
to the pipes as possible. Fig-. 98 shows two systems of pipe 
connections, one where the steam or flow enters the coils 
from above the benches and the other where it enters from 
below, the return in each case being- at the lowest point. 
These bench coils could be run along the wall with equal 
satisfaction. 

Application. — Given an even-span greenhouse 25 ft. wide, 
100 ft. long and 5 ft. from ground to eaves of roof, having 
the slope of the roof with the horizontal 35°. The ends to 
be glass above the eaves line. What amount of hot -water 
radiation with average water temperature 170°, interior 
temperature 70° and outside temperature 0°, and what 
amount of low pressure steam radiation should be installed? 

Length of slope of roof = 12.5 -^ cos. 35° = 15.25. Area 
of glass = 15.25 X 100 X 2 + 2 X 12.5 X 8.8 = 3270 sq. ft. 
Area of wall = 5X100X2 + 5X25X2 = 1250 sq. ft. 
Glass equivalent = 3270 + .25 X 1250 = 3582.5 sq. ft. Rw — 
.32 X 3582.5 = 1146 sq. ft. Rs = .21 X 3582.5 = 752 sq. ft. 
From Table XVL Rw = 3582.5 -^ 2.81 = 1270 sq. ft. Rs = 
3582.5 -^ 5 = 716 sq. ft. *Check with last column of Table 
XVI. 

References. — Jour. A. S. H. & V. E. Heating a Conserva- 
tory and Greenhouse, July 1916, p. 29. Metal Worker. Design 
of Greenhouse Heating Plants, July 9, 1915, p. 44. Heating 
Equipment for Large Greenhouse, Jan. 1, 1915, p. 66. Domes- 
tic Engineering. The Hot Water Heating in Highland Park 
Greenhouse, Sept. 21, 1912, p. 292. 

106. The Theoretical Determination of Pipe Sizes: — The 
theoretical determination of pipe sizes for small hot water 
and steam systems has always been more or less unsatisfac- 
tory because of the difficulty in estimating the friction of- 
fered by different combinations of piping. The following 
analysis is illustrative and does not account for friction. 

Assume a hot loater system. Figs. 101-104, having water 
temperatures entering and leaving the radiators 180° and 
160° respectively. Since one pound of water in passing 
through each radiator gives off 20 B. t. u., the radiators in 
the Living Room (91 sq. ft.) and Chamber 2 (70 sq. ft.) will 
require 91 and 71 gallons of circulating water per hour 
(check the values), or approximately one gallon .of water per 



HOT WATER AND STEAM HEATING 181 

square foot of radiating surface per hour. This is a general state- 
ment which will be true for any low pressure hot water 
system with 20 degrees temperature drop. With the amount 
of water required per hour obtain the velocity due to the 
unbalanced columns and find by division the area of the pipe. 
Assume the radiator in the Living Room to have a 5-ft. 
static head and that in Chamber 2 a 15-ft. head. Having 
the water temperature in the flow risers 180° and in the re- 
turn risers 160° (good values in practice), the heated water 
in the flow risers weighs 60.5567 pounds per cubic foot, while 
that in the return risers weighs 60.9697 pounds per cubic 

W — W 

foot. The motive force is f = g X , where g is the 

W + W' 

acceleration due to gravity, W is the specific gravity 
(weight) of the cooler column and W is the specific gravity 
(weight) of the warmer column. Substitute f for g in the 
velocity equation and obtain 






(60) 



Inserting values W, W and 7^ = (5 and 15) feet, we have 
v = 1.05 f. p. s. (Living Room) and 1.8 f. p, s. (Chamber 2). 
Velocities for any other height of column and for other tem- 
peratures may be obtained in like manner. Reducing the 91 
and 71 gallons to cubic inches and dividing by the velocity 
per hour in inches gives .46 sq. in. and .21 sq. in. respec- 
tively. Since pipe sizes are measured on the internal diam- 
eter these values are equivalent to pipes of %- and i/^-inch 
respectively. For the determination of pipe sizes, friction included, 
see Art. 197. The application of friction equations to pipes 
of 4 inches or more in diameter is very satisfactory but for 
small pipes, such as are found in the average house heating 
plant, it is still the custom to use tables of sizes based upon 
what experience has shown to be good practice. Such tables 
may be found in the Appendix. From Table 34 we find the 
branches and risers to the two radiators under consideration 
to be 1^- and 1-inch respectively. 

In steam systems where the heating medium is a vapor and 
subject in a lesser degree to friction, the discrepancy be- 
tween the theoretical and the practical sizes of a pipe is not 
as great as in hot water. Each pound of steam at 220° in 
condensing gives off about 970 B. t. u. To supply the heat 



182 



HEATING AND VENTILATION 



loss of the Living- Room, 15267 B. t. u., requires 15.8 pounds 
of steam per hour = .26 pounds of steam per square foot of 
radiation. As a general statement use one-fourth of a pound of ' 
steam per square foot of direct radiation per Tiour. To check this 
stateinent, each square foot of steam radiation gives off 250 
B. t. u. per hour and will condense 250 -^ 970 = .258 pounds 
of steam. 

The volume of the steam per pound at the usual steam 
heating pressure 17 to 18 pounds absolute is 23 cubic feet. 
Since the above radiator requires 15.8 pounds per hour there, 
will be needed 23 X 15.8 = 363 cubic feet per hour. With 
the velocity of the steam in the pipe lines 15 feet per second 
(900 ft. per min. about one-seventh that allowed for power 
plant machinery. Taken as a fair approximation for small 
pipes) the area of the pipe will be 363 X 144 -4- 54000 = 
.97 sq. in. = 1%-in. diameter. For two-pipe connections a 
1-inch pipe would be considered good practice, but for one- 
pipe connections where the condensation is returned against 
the steam, a 1^/4 -inch pipe would be required. 

See Tables 38, 39, 40 and 41, Appendix, for sizes and 
capacities of pipes carrying steam. For a discussion of 
steam pipe sizes by rational equation, including friction, see 
Art. 197. 

107. Proportioning Pipe Sizes for a Heating System; — 

Begin at the farthest radiator and proceed toward the boiler 
as shown in the following tabulations. 



60— 



-80— 




Fig-. 99. 



HOT WATER AND STEAM HEATING 



183 



Basement Main Two-Pipe Hot Water System (Pig-. 99). 
TABLE XVII. 

L. P. = Low Pressure Open Tank System. H. == Honeywell System. 





Branch 






Branch 








from Kad. 


Riser 


from Main 


Main 


Sq. ft. 




















L. P. 


H. 


L. P. 


H. 


L. P. 


H. 


L. P. 


H. 


60 




% 


A 1 


A % 










80* 


IV2 


ly* 


B IV2 


B 1% 


C 2 


iy2 






140 














D 2y2 


D 2 


60 


1 


% 


E 1 


L % 










70 




% 


F iy2 


F 1 










70 


1% 


1 


G 1% 


G 1 


H lya 


iy2 






340 














1 2y2 


1 2y2 


80 




% 


J 1 


J % 










70 




% 


K 1% 


K 1 










100 


ly* 


1 


L 1% 


L 1 


M 2 


2 






590 














N3 


N 2y2 



* Find of supply line, first floor radiator given advantage 
Return branches same as supply branches 
Return Main reversed. 












p 




Q 




L. P. 




H. 


L. P. 






H. 


L.P. 


H. 


2 


2 


2y2 




2y2 


3 


2y2 



Basement Main Two-Pipe Steam System. 
Sealed returns. (See Fig-. 99). 



TABLE XVIII. 





Branch 






Branch 




Sq. ft. 


from Rad. 


Ri 


=er 


from Main 


Main 


S 


R 


S 


R 


S 


R 


S 


R 


60 


IV4 




A 1% 












80 


iy2 




B iy2 




C 2 


iy2 






140 














D 2y2 


Q 2 


60 


iy4 




E 114 












70 


iy4 




F iy2 


iy4 










70 


ly* 




G iy4 




H 2 


iy2 






340 














I 3 


P 2 


80 


iy4 




J ly* 












70 


iy4 




Kiy2 


1% 










100 


iy2 


iy4 


L iy2 


1% 


M 2 


iy2 






590 














N 3 


iy2 



184 



HEATING AND VENTILATION 




->- 73 Soi/er- 

-pig. 100. 

Basement Main One-Pipe Steam System (Fig. 100). 

TABLE XIX. 



Sq. ft. 


Brancii 
from Rad. 


Riser 


Brancli 
from Main 


Main 


60 


W2 


A 11/2 






80 


11/2 


B 11/2 


2 




140 








D2y2 


60 


IV2 


E 11/2 






TO 


11/2 


F 2 






70 


11/2 


G 11/2 


H 2 




340 








I 3 


80 


11/2 


J 11/2 






70 


11/2 


K 2 






100 


2 


L 2 


M2y2 




,590 








N 3 



Return line to boiler same as dry return for two-pipe 
system, in this case 2-inch. 

108. Pitcli of Mains: — The pitch of the mains should be 
not less than 1 inch in 10 feet for hot water systems and 1 inch in 
30 feet for steam systems. Greater pitches than these are desir- 
able but are not always practicable. In hot water plants the 
one-pipe main has its highest elevation above the boiler and 
drops to the far end of the line, with the lowest point where 
it enters the boiler, the two-pipe basement main and return 
each pitch upward from the boiler to the end of the run and 
the attic main has its hig-hest point at the top of the attic 
riser. The two pipe systems, both basement and attic mains, 
should have the supply and return reversed, i. e., the return 



HOT WATER AND STEAM HEATING 185 

should beg-in at the first radiator served by the supply. In 
steam plants the supply main pitches downward toward the 
far end of each run, the highest point being above the boiler. 
The return main pitches downward from the end of each run 
toward the boiler. 

109. Liocation and Connection of Radiators: — In locating 
radiators, it is usual to place them along the outside or ex- 
posed walls and when allowable, under the windows. This 
is probably the best location although some difference of 
opinion has been expressed on this point. When so placed 
the cold current of air from the window interferes with the 
warm upward current from the radiator and breaks it up. 
A series of tests reported in the Journal of the A. S. H. and 
V. E., July 1916, page 65, by a special committee of the 
society, shows that next to the center of the room the floor 
line near the outside wall is the most effective location. In 
building's of several stories, the radiators should be ar- 
ranged as far as possible in tiers, one vertically above an- 
other, thus reducing the number of risers and offsets. In 
one-pipe and two-pipe steam systems any number of radi- 
ators may be connected to the same riser, providing the riser 
is proportioned to the radiation supplied. In the two-pipe 
systems a water seal between each radiator and the return 
riser is advisable. This insures each radiator to be an inde- 
pendent unit in its action. In two-pipe hot w^ater systems 
several radiators may have common flow and return risers 
as in steam systems providing the risers are carefully pro- 
portioned to the radiation. This is not always a safe plan. 
Under such an arrang-ement the upper radiators frequently 
have the advantage and rob the lower radiators. To be sure 
upon this point, either one of two methods may be employed: 
(1) offset the riser (See radiators C and D, Fig. 50); (2) 
isolate the returns (See radiators A and B, Fig. 49). 

The connections from the risers to the radiators should 
be slightly pitched for drainage. They may be run along- 
the ceiling below the radiator or above the floor behind the 
radiator. Connections should be at least 2 feet long to give 
flexibility for the expansion and contraction of the riser. 
For sizes of radiator connections see Table 41, Appendix. 

110. General Application: — Figs. 101-104 show an illus- 
trative layout of a hot water plant (See residence Art. 62). 
Because of the siinilarity between hot water and steam in- 



186 HEATING AND VENTILATION 

stallations, the former only will be outlined. In making 
the layout of such a system, first locate the radiators in the,, 
rooms. This should be done with the advice of the owner' 
who may have particular uses for certain spaces from_ which 
radiators must be excluded. Calculate the heat loss for each 
room, including exposure losses, ventilation losses, etc., and 
tabulate the results (See first column Table XX. Taken 
from Table XII). Calculate the square feet of radiation 
(Equation 51) and select the type, height and number of sec- 
tions of each radiator from Table XIII. Check the radiator 
lengths and determine whether or not a radiator of such 
length will fit into the chosen space. If this can not be done, 
a radiator of greater height or number of columns must be 
selected. Branches from main to riser and riser sizes are 
usually the same although on a long branch it may be found 
necessary to put in a branch one size larger than the riser. 
Also, the branch from the riser to the radiator and the radi- 
ator connection sizes are usually the same excepting where 
there may be unusual conditions to meet, in which case the 
branch may be made one size larger than the standard con- 
nection. For commercial sizes see Tables 38 and 40, Appen- 
dix. Column in Table XVII marked "Radiators installed" 
should read "number of sections, height in inches and number 
of columns" (See Living Room = 18-38-3). 

Locate the risers on the second floor plan and transfer 
these locations to the first floor and basement plans. Treat 
the first floor risers in a similar manner. The basement 
plan will then show by small circles the location of all risers. 
This arrangement will aid greatly in the planning of the 
basement mains. The principal features in the layout of the 
basement mains should be simplicity and directness. If the 
riser positions show approximately an even distribution 
around the basement, it may be advisable to run the main 
as a complete circuit system. If the riser positions show 
aggregations at two or three localities, two or three mains 
running directly to these localities are the most desirable. 
As an illustration the basement plan shows three clusters 
of riser ends, one under the kitchen, another under the study, 
and a third along the west side of the house. This condition 
immediately suggests three supply mains. That toward the 
north supplies the bath, chamber 4 and the kitchen, a total 
of 161 square feet. Being approximately 13 ft. long, a l^^- 



HOT WATER AND STEAM HEATING 



187 



inch main will carry the radiation. That toward the east 
supplies chamber 1, the hall and the study, a total of 225 
square feet, which can be carried by a 2-inch pipe. That 
toward the west side of the house supplies chamber 2, cham- 
ber 3, the living- room and the dining room, a total of 277 
square feet, which should have a 2-inch main. 

In hat water work, as well as in steam, it is customary 
to connect supply branches (especially first floor branches) 
from the top of the mains, thus aiding the natural circula- 
tion. If this is not possible connect at 45 degrees. With a 
short nipple, a. 45 degree elbow and a horizontal run of 2 to 
3 feet this arrangement has sufficient flexibility to avoid 
expansion troubles. First floor radiators and those farthest 
from the boiler should be given the advantage of top 
branch connections and larger proportional pipe sizes. 

In the selection of the hoUer estimate the grate size from 
the total heat loss and check by the catalog rating in square 
feet of radiation. With soft coal at 13000 B. t. u. per pound, an 
efficiency of 60 per cent, and 5 pounds of coal per square 
foot of grate per hour there will be needed (110574 X 144) -^ 
.60 X 5 X 13000 = 408 sq. in. grate area. Adding 50 per 
cent. (Art. 100) for soft coal gives 612 sq. in. This agrees 
with Am. Rad. boiler W-19-6, 1250 sq. ft. rating. Checking 
radiation equivalent = 663 sq. ft. calculated radiator surface + 
25% mains, risers, etc., = 829 sq. ft, total radiation + 50 per 
cent. = 1236 sq. ft. 

TABLE XX. 



Living- R. _. 
Dining R. _. 

Study 

Kitchen 

Reception H. 
Chamber 1 _ 
Chamber 2 _ 
Chamber 3 _ 
Chamber 4 _ 
Bath 



Heat 

loss, H 

from 

Table 

XII 



15267 



12948 
12828 
14059 
10583 
11770 
9092 
8892 
5179 



Rad. 

Surface 
R = 
.OOQH 



77 
84 
63 
71 
55 
53 
31 

663 



Radia- 
tors 
installed 



18-38-3 
16-26-3 
19-14-F 
16-38-3 
17-38-3 
17-26-3 
li)-26-3 
15-2&-3 
15-26-3 
&-26-3 



Length 
of Rad. 
installed 



Branches 

and 
Risers. 
Supply 

and 
Return 



IV4 

1 

IV4 

ly* 

1 
1 

1 
1 



Rad. 
connec- 
tion 



IV4 
1 

1% 
IV4 
1% 
1 
1 
1 
1 
% 



188 



HEATING AND VENTILATION 



Z7'-e-- 



'00 



HN 



a 



\m 



r 



#L 




l5'-9ir 



-Hl2>- 9-9i 

32-7" 



Foundation Plan 

CCILINS 7' 



Fig-. 101. 



HOT WATER AND STEAM HEATING 



189 




Fig-. 102. 



190 



HEATING AND VENTILATION 



^LT 28'X34: il llJ28'y'34-" 




(9-26-3 

oiiiiiiniiiii* 



Second Floor Plan 

CEILING 9' 
-Z. 



Fig. 103. 



HOT WATER AND STEAM HEATING 191 




19-24-3 

MAIN AND RISER LAYOUT. 
Fig-. 104. 

111. Insulating Steam P.ipes: — In all heating systems, 
pipes carrying- steam or water should be insulated to reduce 
the heat losses unless these pipes are to serve as radiating 
surfaces. In most plants the heat lost through these unpro- 
tected surfaces, if saved, would soon pay for first-class in- 
sulation. The heat transmitted to ordinarily still air through 
one square foot of the average horizontal wrought iron pipe 
is as great as 2.65 B. t. u. per hour, per degree difference of 
temperature between the inside and the outside of the pipe. 



192 HEATING AND VENTILATION 

Assuming- this to be 2.5, with steam at 100 pounds gage and 
air at 80°, the heat loss is (338 — 80) x 2.5 = 645 B. t. u. pei't 
hour. With steam at 50, 25 and 10 pounds gage respectively 
this will be 545,467 and 397 B. t. u. If the pipes were located 
in an atmosphere having decided air currents this loss w^ould 
be rnuch greater. The average unprotected low pressur 
steam pipe will probably lose between 350 and 400 B. t. u. 
per square foot per hour. Assuming this to be 375 and ap 
plying it to a 6-inch pipe 100 feet in length, for a period of 
240 days at 20 hours a daj', we have a heat loss of 171 X 
375 X 240 X. 20 = 307800000 B. t. u. With coal at 13000 B. t^ 
u. per pound and a furnace efficiency of 60 per cent, this will 
be equivalent to 39461 pounds of coal, which at $3.50 per ton- 
will amount to $69.05. From tests that have been run on the 
best grades of pipe insulation, it is shown that 80 to 85 per 
cent, of this heat loss may be saved. Taking the lower value 
there would be a financial saving of $55.24 if covering were 
used. If a good grade of pipe covering installed on the pipe 
is -worth $85.00 the saving in one and one-half year's, time 
would nearly pay for the covering. 

To be effective, insulation should be cellular but should 
not permit air circulation. Small voids filled with still air 
are among the best insulators, consequently hair felt, min- 
eral wool, eiderdown and other loosely woven materials are 
very efficient. Some insulating materials disintegrate after 
a time and lose their form but many patented coverings have 
good insulating qualities as well as permanency. Most 
patented coverings are 1 inch in thickness and may or may 
not fit closely to the pipe. A good arrangement is to select 
a covering one size larger than the pipe and set this ofC from 
the pipe by spacer rings. The air space between the pipe and 
the patented covering renders the covering more efficient. 
Table 50, Appendix, gives the results of a series of experi- 
ments on pipe covering, obtained at Cornell University under 
the direction of Professor Carpenter. 

112. Water Hammer: — When steam is admitted to a 
pipe that is full of water, it is suddenly condensed causing 
a sharp cracking noise. The concussion produced may be- 
come so severe as to crack the fittings or open up the joints. 
The noise is due to the sudden rush of water from the sur- 
rounding space in an endeavor to fill the vacuum produced 
by the condensed steam. Steam at atmospheric pressure 



HOT WATER AND STEAM HEATING 193 

occupies 1650 times the volume of the water that formed it, 
so when this steam is suddenly condensed a very high vac- 
uum is produced which caused a relatively high velocity in 
the water adjacent to it. Steam should always be admitted 
very slowly to a cold pipe or to one filled with water. 

Water hammer is frequently produced in water mains 
by suddenly stopping the stream of flowing water. For a 
theoretical discussion of this subject see Church's Hydraulic 
Motors, page 203. To find the approximate pressure p in 
pounds per square inch, produced by water hammer when 
r = velocity of the water in feet per second, use p — 63 r. 
Also, to find the least time in seconds required in closing a 
valve on a water main that water hammer may be avoided, 
divide twice the length of the pipe stream by 4670 (See ref- 
erence above). To illustrate. Water in a water main 500 
feet long is fiowing at the rate of 10 feet per second. If the 
water movement were suddenly stopped by closing the valve 
at the end of the main the pressure produced at the valve 
would be approximately 630 pounds per square inch. The 
least time of closing the valve to avoid water hammer would 
be 1000 -f- 4670 = .21 second. 

113. Returiiiiisg- the Water of Condensation from a liO^v 
Pressure Steam Heating- System to the Boiler; — In returning 
the water of condensation to a boiler four methods are in 
use; gravity, steam traps, steam loops and steam or electric 
pumps. The gravity system is the simplest and is used in all 
cases where the radiation is above the level of the boiler 
and where the boiler pressure is used in the mains. In a 
gravity return no special valves or fittings are necessary 
but a free path with the least amount of friction in it is 
provided between the radiators and some point on the boiler 
below the water line. No traps of any kind should be placed 
in this return circuit. 

All radiation should be placed at least 18 inches aoove 
the water line of the boiler to insure that the water will not 
back up in the return line and fiood the lower radiators. 
Flooding usually takes place through the return main and 
is the result of a restricted steam main. It may be due to 
a boiler which is too small and has to be forced thus caus- 
ing siphonage. Where the radiation is below the water line, 
or where the pressure in the mains is less than that in the 
boiler, some form of steam trap or motor pump must be put 



194 



HEATING AND VENTILATION 



in with special provision for returning- the water of conden- 
sation to the boiler. Two kinds of traps may be had, low 
pressure and hig-h pressure. The first is well represented by 
the bucket trap, Fig-. 105, and the second by the Bundy trap, 
Fig-. 106. The action of these traps is as follows: Bucket 
trap. — Water enters at D and collects around the bucket 





Fig. 105. 



Fig. 106. 



which is buoyed up against the valve. Water fills in and 
overflows the bucket until the combined weight of the water 
and bucket overbalances the buoyancy of the water. The. 
bucket then drops and the steam pressure upon the inside, 
acting- upon the surface of the water, forces it out through 
the valve and central stem to outlet B. When a certain 
amount of w^ater has been ejected the bucket again rises and 
closes the valve. This action is continuous. Bundy trap. — 
Water enters at D through the central stem and collects in 
bowl A which is held in its upper position by a balanced 
weight. When the water collects in the bowl sufficiently to 
lift the weight, the bowl drops, valve E opens, and steam is 
admitted to the bowl thus forcing the w^ater out through the 
curved pipe and valve E. This action is continuous. 

Each trap is capable of lifting the water 2.4 feet above 
the trap for each pound of differential pressure. Thus, for 
a pressure of 5 pounds gage within the boiler and 2 pounds 
gag-e on the return, the water may be lifted 7 feet above the 
trap, or to the top of an ordinary boiler. This is not suffi- 
cient, however, to admit the water into the boiler against 
the pressure of the steam. A receiver should be placed here 
to catch the water from the separating trap and deliver it to 
a second trap above the boiler, which in turn feeds the 
boiler. Live steam is piped from the boiler to each trap, but 
the steam supply to the lower trap is throttled to give only 
enough pressure to lift the water into the receiver. A sys- 



HOT WATER AND STEAM HEATING 



195 



tern connected in this way is shown in Fig. 107. Here the 
receiver and trap are combined. Traps which receive' the 
water of condensation for the purpose of feeding- the boiler 
are called return traps and sometimes work under a higher 

pressure of steam than the 
separating traps. Many dif- 
ferent kinds of traps are in 
general use but these will 
illustrate the principle of 
operation. 

Avery simple arrangement 
and a very difficult one to 
operate satisfactorily, is the 
steam loop (Fig. 108). The 
water of condensation from 
the radiators drains to re- 
ceiver A, which is in direct 
communication with riser B. 
Drop leg D, being in com- 
munication with the boiler 
through a check valve which 
the lowest point, is filled 
with water to point X sufficiently high above the water 
' ■ fl^ 

AIR VALVE 




opens 



VtNTPIft TO ASH PIT 



Fig. 107. 
toward the boiler at 




Fig. 108. 



196 HEATING AND VENTILATION 

line of the boiler that the static head balances the differen- 
tial pressure between the steam in the boiler and that in the 
condenser. Horizontal pipe C serves as a condenser which 
produces a partial vacuum and lifts the water from the re- 
ceiver. This water is not raised as a solid body, but as slugs 
of water interspersed with quantities of steam and vapor. 
The water in A is at or near the boiling point and the re- 
duced pressure in B re-evaporates a portion of it which, in 
rising as a vapor, assists in carrying the rest of the water 
over the gooseneck. When the condensation in D rises above 
point X, the static pressure overbalances the differential 
steam pressure, and water is fed to the boiler through the 
check. 

To find the location of point X above the water line in 
the boiler, the following will illustrate. Let the pressure in 
the boiler, condenser and receiver be respectively 5, 2 and 4 
pounds gage; then the differential pressure between the 
boiler and condenser is 3 pounds per square inch. If the 
weight of one cubic foot of water at 212° is 59.76 pounds, the 
pressure is .42 pound per square inch for each foot in height, 
i. e., one pound differential pressure will sustain 2.4 feet of 
water. With a pressure difference of 3 pounds this gives 
3 -=- .42 = 7.2 feet from the water level in the boiler to point 
X, not taking into account the friction of the piping and 
check which would vary from 10 to 30 per cent. Assuming 
the friction to be 20 per cent, we have the static head = 
7.2 ^ .80 = 9 feet to produce motion of the water toward the 
boiler. 

The length of riser pipe B and its diameter depends upon the 
differential pressure between the condenser and the receiver, 
and upon the rapidity of condensation in the horizontal. A 
differential pressure of 2 pounds will suspend 2 X 2.4 = 4.8 
feet of solid water, but the specific gravity of the mixture in 
this pipe is much less than that of solid water. For the sake 
of argument let it be 20 per cent, of that of solid water, in 
which case we would have a possible lift, not including fric- 
tion, of 5 X 4.8 = 24 feet. This is 24 — 9 = 15 feet below 
the water level in the boiler. The diameter of the riser may 
vary for different plants, but for any given plant the range 
of diameters is very limited. These are found by experiment. 



HOT WATER AND STEAM HEATING 



197 



. A drain cock should be placed in the receiver at the 
lowest point. When cold water has collected in the receiver 
it is necessary to drain this water to the sewer before the 
loop will work. An air valve should be placed at the top of 
the gooseneck to draw ofE the air. If the horizontal pipe is 
filled with air, there will be no condensation and the loop 
will refuse to work. Never connect a steam loop to a boiler 
in connection with a pump or any other boiler feeder. To 
determine whether a loop is working place the hand on the 
horizontal pipe. If this is cold it is not working. 

The steam loop is used with success in factories and 
manufacturing plants in returning steam separator drips to 
boilers. In a series of experiments conducted in 1910, the 
condensation from four 100 square foot radiators was lifted 
21 feet to a coil condenser and delivered by gravity to a 




Fig. 109. 



pressure tank located 5 feet above the receiver and main- 
tained at a pressure 1% pounds above the receiver pressure. 
Much experimentation will be necessary before the riser 
diameters and the condenser surfaces will be properly pro- 
portioned to be of general usefulness in heating systems. 
The last method mentioned for feeding condensation to 
the boiler was a steam or electric pump. The operation of the 
steam pump is fully discussed in Art. 186. An electric motor- 
pump with its receiver and pipe connections is shown in Fig. 
109. Its operation is very similar to that of the steam pump. 



198 



HEATING AND VENTILATION 



When the returning- condensation fills the receiver to a cer- 
tain level a float regulator starts the motor and pumps the 
water from the receiver to the boiler. When the -water level 
drops the operation is reversed and the pump is automat- 
ically stopped. The motor pump is used on low pressure 
heating systems where the water of condensation from the 
coils and radiators drains below the boiler. If the boiler 
pressure were high the ordinary steam pump would be pre- 
ferred. Where the pressure within the boiler is near that in 
the return main the operation of such a piece of apparatus 
is less expensive than that of the steam pump. 

114. Hot Water Heating for Tanks and Pools! — The de- 
termination of the amount of heat transmitted, the amount 
of water heated and the square feet of coil surface needed 
for heating- water by the use of immersed steam coils, fol- 
lows closely the -work given under hot w^ater heating, Art. 
101, Equations 49 and 50. From experiments conducted by the 
American Radiator Co., at the Institute of Thermal Research, 
the amount of heat transmitted in B. t. u. per hour, K [ts — 
{ta -f /&) -f- 2], through iron and brass pipes from steam 
(up to 10 lbs. g-age) to water, allowing an efficiency of 50 
per cent, for fouling of the pipes is: 



Diff. between steam temp, and 

av. temp, of water, 

degrees 


50 


70, 


100 


150 


200 


Brass 


720O 
4500 


12800 
8000 


24000 
loOOO 


48000 
30000 


80000 


Iron 


50000 



Knowing the amount of water to be heated through a 
given temperature difference, the coil surface and the steam 
condensed may be determined. 

Application. — Required to heat 3000 pounds of water per 
hour from 60° to 90° with steam at 5 lbs. gage pressure. 
How many pounds of steam will be condensed per hour and 
how many square feet of iron coil surface will be necessary. 

Result.— Steam temperature, 227°; average temperature 
of water, 75°; temperature difference, 152 degrees; heat g^iven 
to water, 90000 B. t. u.; steam condensed, 92.2 lbs.; coil sur- 
face, 3 square feet. 



HOT WATER AND STEAM HEATING 199 

115. Suggestions for Operating Hot Water Heaters and 
Steam Boilers: — Before firing up in the morning examine the 
pressure gage to see if the system is full of water. If there 
is any doubt, inspect the water level in the expansion tank. 
If it is a steam system, examine the gage glass and try the 
cocks to see if there is sufficient water in the boiler. 

See that all valves on the water lines are open. On the 
steam system try the safety valve to make sure that it is 
free. Also see if the pressure gage stands at zero. 

In starting a fire under a cold boiler it should not be 
forced but should warm up gradually. 

For suggestions on firing read Art. 77. 

In a boiler or heater using the same water continuously 
(the best plan) there will be little need of cleaning the in- 
side of the boiler. Where fresh water is used frequently 
soft water should be used. Where hard water is used the 
boiler should be blown off and cleaned once or twice a month. 

Never blow off a boiler while hot or under heavy pres- 
sure. 

Inspect the pressure gage, glass gage, waiter cocks and 
thermometers frequently. 

In case of high steam pressure in a steam system, cover 
the fire with wet ashes or coal and close all the drafts. Do 
not open the safety valve. Do not feed water to the boiler. 
Do not draw the fire. Keep the conditions such as to avoid 
any sudden shock. After the steam pressure has dropped 
sufficiently examine the safety valve. 

Excessive pressure may be caused by the sticking of the 
safety valve in the steam system, or by the stoppage of the 
water line to the expansion tank in the hot water system. 
The safety valve should never be allowed to lime up, and the 
expansion tank should always be open to the heater and to 
the overflow. 

In case of low water in a steam system, cool the fire, 
lower the pressure to atmosphere and fill the boiler. 

When leaving the fire for the night shake down and 
bank as stated in Art. 77. 



CHAPTER IX. 



MECHANICAL, VACUUM HEATING SYSTEMS. 



'i\ 



116. Return Line Systems. — Air and Condensate Com- 
bined: — The term "vacuum heating" may properly be ap- 
plied to that class of heating- systems having a continuous 
negative pressure within the return main, the pressure 
within the radiators being controlled by the interposition 
of some form of thermal or float valve between the return 
main and the radiators. The vacuum may be produced by 
pumps or ejectors. In point of design this is the extreme 
in its departure from the low pressure gravity system and 
has the following advantages over it: 

1. A positive and rapid return of the water of con- 
densation. 

2. In case of improper alignment of main and retunj 
pipes the negative effect of water and air pockets . is r 
duced to a minimum. 

3. Radiation at low levels may be drained by main- 
taining a vacuum in the return line proportional to the lift 
of the water of condensation. 

4. Smaller return pipes may be used than are used on 
the ordinary gravity systems. 

5. A continuous withdrawal of the entrained air from 
the radiators with the water of condensation. This insures 
a high efficiency of all the heating surface. This statement 
may not hold good for high radiators (36 to 48 inch) on the 
extreme end of a long heat run. On such radiators, air valves 
may be necessary. 

6. This system is especially adapted to the use of ex- 
haust steam with its extra large air and water content, 

7. Comparative freedom from pounding and water ham- 
mer. 

On the other hand there is an additional cost in main- 
taining the vacuum, and its use is restricted in small plants 
because of the extra cost of installation and superintendence. 

Mechanical Vacuum systems of heating are frequently in- 
stalled in connection with lighting or power units in which 



MECHANICAL VACUUM HEATING 



201 



case the exhaust steam may be used to supplement the live 
steam for heating-. This substitution results in a great 
economy for the plant. A diagrammatic view showing 
the principal apparatus involved in such a plant is shown 
in Fig. 110. Live steam is connected to the power units and 
to the heating main, the latter through a pressure reducing 
valve to be used only when exhaust steam is insufficient. 




rECO WATER 
HEWER 



|cONDEN5CR[ 
CtJlN. PUMP[I3=a 



Fig. 110. 



Exhaust steam from the power units is connected to the 
heating main and to the feed water heater. This exhaust 
steam line opens to the atmosphere through a back pres- 
sure valve which is set at the desired pressure for the sup- 
ply steam. Oil separators remove the oil from the exhaust 
steam and deliver it to the oil traps. Boiler feed pumps 
and vacuum pumps, with the accompanying valves and 
governing appliances, complete the essentials of the power 
room equipment. 

The steam supply to the heating system is piped to 
radiators and coils in the ordinary way, with or without 
temperature control. Thermostatic valves, or equivalent, 
are placed at the return end of each radiator and coil, and 
the returns from these are brought together in a common 
return which leads to the vacuum pump or ejector. The size 
of the return pipe and specialty valve for any one unit is 



202 



HEATING AND VENTILATION 



usually i-^-inch, increasing in size as more radiating- units 
are taken on. Horizontal steam mains usually terminate in 
a drop leg which is tapped to the return 8 to 15 inches above 
the bottom of the leg. Each rise in the system has a drop 
leg at the lower end of the rise. These points and all others 
where condensation and dirt may collect are drained through 
special separator valves to the return. Steam is carried in 
the main slightly above atmospheric pressure and just 
enough vacuum is maintained on the return to insure posi- 
tive and noiseless circulation. In many cases where special 
lifts are required, these return systems are run under pres- 
sures 6 to 10 inches of mercury below atmospheric pressure. 
Under such conditions water may be lifted from 6 to 10 feet. 
Either closed or open feed water heaters may be used. 

When water of condensation at 212° or above is re- 
leased from the radiator through the vacuum valve to the 
returns with pressvire below atmosphere, the result is a very 



EXHAUST TO atmosphcee; 




ENGINE EXHAU5T 



g. 111. 



quick withdrawal and a partial re-evaporation of the water 
into steam or vapor at the lower pressure. If large amounts 
of condensation were thus released at one time, the vacuum 
would be temporarily broken, but being divided into a large 
number of small units having no regularity in the time of 
action, there is little difficulty. Although the vacuum is 
supposed to extend only from the pump to the vacuum valve, 
it may extend to within the radiator if the vacuum valve is 
set for a constant discharge. Such an arrangement cannot 



Jl 



MECHANICAL VACUUM HEATING 203 

be justified from the standpoint of economy, since the latent 
heat of all the leakage steam is lost from the heating system 
and thrown away. Just before entering the vacuum pump, 
the steam and water vapor mixed with the return water 
may be condensed by a spray of cold water. This spray 
assists in increasing- the vacuum. From the vacuum pump 
the returns go to a feed water heater (open or closed) and 
from this by a boiler feed pump back to the boiler. The 
Webster system, shown in detail in Fig. Ill, is a typical repre- 
sentative of this class. In all essential features this figure 
may stand for a number of others, among them the Dunham, 
the Bishop and Babcock, the Illinois and the Automatic. For 
comparative sizes of gravity and mechanical vacuum return 
pipes see Table 43, Appendix. 

117. Air Line Systems. — Air and Condensate Separate: — 
Representing this type of heating is the so-called Paul 
system. It is usually installed as a one-pipe system, fed 
from overhead supply and drained to a wet return, although 
it may be connected up as a two-pipe system or fed from 
a basement supply. The air pump handles the water of con- 
densation but is not installed as a vacuum producing agent. 
The vacuum in the air line connecting with the air valves 
at the radiators, is produced by a steam, air or hydraulic 
ejector which discharges directly into the atmosphere, into 
the atmospheric end of the exhaust heating main or into a 
secondary radiator where a separation is made, the water 
dropping to a receiver to be further used and the air ex- 
hausting to the atmosphere. This system differs from the 
ones mentioned in two essential points; first, the vacuum 
effect is applied at the air valve and the flow of water of 
condensation is independent of the vacuum; second, the 
vacuum effect is produced by the aspirator principle using 
water, steam or compressed air as motive power. The 
vacuum is supposed to extend only to the air valve at the 
radiator, but if desired this valve may be adjusted so that 
the vacuum may have an effect within the radiator. The 
layout of the system for large plants is about that shown 
in Fig. 112. This system is especially adapted to small 
plants having one-pipe complete circuit mains, because of 
its effectiveness in removing air from one-pipe radiators. 
When thus used the pump is omitted and the condensate 
flows direct to the boiler by the one-pipe gravity method. 



204 



HEATING AND. VENTILATION 




Fig. 112. 

Fig. 113 shows typical vacuum connections between one-pipe 
and two-pipe radiators and the exhauster. Where electric- 



VACUUn AIR 
LIME 



STEAM IMLET 



TO preE tvER . s^^:f>s:^ 

OR RETURIN B— J*— a> 




'''//////y/////////m 



TOArnOSPHERE 



Fig. 113. 



MECHANICAL VACUUM HEATING 



205 



current is available exhausting may be done by the use of 
an electric motor pump. 

.118. Vacuum Pumps: — The satisfactory operation of 
vacuum heating- systems depends upon the effective removal 
of air and water from the system. Reciprocating pumps 
(modified types of the direct acting piston pump) are gen- 
erally used in producing the vacuum. Fig. 114 is a sec- 
tional view of the valve governing the action of the Ameri- 



Tr/pf^rt tjj SteamPfpe /?e//efHo/e 




Sect/on afffS 
f Exhaust P/pe 
Fig. 114. 

can-Marsh Vacuum Pump. Steam enters the chest through 
the pipe at B and a small amount passes through the port 
C to the auxiliary Valve B. Auxiliary Valve Z) is operated 
by a lever connected to the crosshead on the piston rod, and 
can be regulated by two adjusting screws. When the piston 
reaches the end of its stroke, steam is admitted by auxiliary 
valve through the small port X outside of the rear head of 
the main valve, forcing it forward to the position shown 
in the figure. When in this position steam travels through 
the steam port E and moves the piston to the opposite end 
of its stroke, the pump exhausting through the passage V 
as shown by arrows. Exhaust from the opposite end of the 
valve escapes through port X' and valve T) to the main ex- 
haust pipe. To hold the main valve in position after the 
auxiliary has placed it, live steam is admitted through bal- 
ancing port (x maintaining hi^h pressure against the outside 
of the head, which more than balances the pressure on the 
inside of this same head owing to the difference of the area 
on either side. Port Y at each end of the valve prevents the 
valve from centering. In any position of the valve one of 
these ports is open to steam pressure and conducts steam 
to the outside of the valve head causing the valve to move 
into operating position. When the piston reaches the for- 
ward end of its stroke the operation is repeated at the for- 



206 



HEATING AND VENTILATION 



ward end of the valve. A few of the sizes and capacities of 
these pumps for the average mechanical vacuum heating- 
system are given in Table XXI. 

TABLE XXI. 
Capacities of Marsh Vacuum Pumps. 







Steam pressure 5 to 10 lbs. 


Steam pressure 


50 lbs. and above 


Not over 2 lbs. back pressure. 
Por discharging- into open receiver 


Size, inches 


Sq. ft. direct rad. 


Size, inches 


Sq. ft. direct rad. 


4x3x6 


1200 


7x3x8 


1250 


4x4x6 


2200 


8x31^x8 


1800 


4x5x6 


3400 


10x4x12 


4000 


4x5x8 


45O0 


12x5x12 


6500 


5x6x10 


8000 


14x6x12 


850O 


5x7%xlO 


12000 


16x71/4x12 


120OO 


6x8x12 


18000 


16x8x12 


15000 


8x10x12 


30000 


18x9x12 


20000 



Two systems of regulation are in common use in connection 
with piston vacuum pumps. In Fig. 115 the pressure in the 
return operates through the governor to regulate the supply 
of steam to the pump, thus controlling its speed. In Fig. 
116 the pressure in the return controls the flow of injection 

JU 




VACUUM PUMP ' 

Fig. 115 




Fig. 116 



water into the suction strainer and hence the rapidity of 
vapor condensation in the return. Either system provides 
automatic control for the vacuum. Injection water for the 
production of vacuum is not a necessity in vacuum returns. 
Systems are operating satisfactorily without it. 

Occasionally it is desirable to have the returns for certain 
parts of heating systems under (lifferent vacuum. As an illus- 



MECHANICAL VACUUM HEATING 



20.7 



tration of this, suppose 
a building- are expected 
pressure and the return 
basement condensate at 
may be accomplished by 
in the branch requirin; 
hig-her line), as shown 



the returns for the radiators within 
to carry condensate at atmospheric 
s from a set of heating coils in the 
four pounds below atmosphere. This 
placing a pressure regulating valve 
g the least negative pressure (the 
by Type D connection in the Web- 




i WATER't.AlR 
RELIEF VALVE 



CONNECT INTO 
TOP or RETURN 



Fig. 117. Fig. 118. 

ester system. Fig. 117. The differential pressure between the 
atmospheric and vacuum lines may be varied to suit any 
condition by the controller valve. A trap and a controller 
valve are applied to each line having a different pressure 
from that in the main suction line. 

Strainers or dirt catchers are installed next the pump on 
mechanical vacuum returns, to protect it from the cutting 
action of the core sand and dirt from the radiators. Where 
large amounts of radiation are grouped, a dirt catcher may 
be placed at the outlet of each group. (See Figs. 115, 116 
and 118). 




SECTION A-A 




Fig. 11! 



208 



HEATING AND VENTILATION 



Centrifugal pumps are being increasingly used on vacuum 
returns where a moderate vacuum only is to be maintained. 
The Nash Hydroturbine (Fig. 119) represents this class. 
The pump consists of independent water and air units 
mounted on the same shaft. The water end is the usual 
centrifugal pump. The air and vapor pump (transverse sec- 
tion) shows a water wheel rotating in an elliptical casing 
partly filled with water. The water as it follows the wheel 
also follows the contour of the casing, this alternately mov- 
ing from and toward the shaft and thus drawing in and 
exhausting continuously and without pulsation. In opera- 
tion the centrifugal pump handles water in coming up to 
speed and continues automatic operation when there is a 
water supply. The air pump however produces continuous 
vacuum, but only at the rated speed. Table XXII gives rec- 
ommended sizes and capacities of this pump. 

TABLE XXII. 
Capacities of Nash Vacuum Pumps. 











Water 










Sq. ft. 




Air 


capacity 










direct 


Diameter 


capacity 


gals. 


Actual 




H. P. 


Size 


equivalent 


orifice 


cubic tt. 


per mm. 


Horse 


R. P. 


of 




radiation 


inches 


per min. 


10 IBs. 


Power 


M. 


Motor 




surface 


vac. 10 In. 




pres. 
180° F. 








A 


800O 


9/64 


6 


11 


.9 


180O 


1 


B 


16O0O 


3/16 


11 


22 


1.4 


1800 


ly?. 


C 


26O0O 


1/4 


19 


35 


2 


1800 




D 


400O0 


9/32 


25 


60 


2.8 


1200 


3 


E 


65O0O 


3/8 


42 


90 


3.9 


1200 






119. Vacuum Specialties: — Classified according to trade 
names these are: 

Return Water Lines — radiator traps, thernio-traps, vacu- 
traps, sylphon traps, radifiers and water seal motors. 

Air Lines — vent valves, thermostatic valves, automatic 
expansion valves and vacustats. 

Regardless of the trade names and the locations of the 
fittings on the systems, they may be classified under three 
heads: 

Type A. Thermostatic valves — those opening and clos- 
ing under the action of heat. Automatic and adjustable. 



MECHANICAL VACUUM HEATING 



209 



Type B. Float valves — those opening and closing- under 
the action of the floatation or the impulse of the water of 
condensation. Automatic. 

Tj'-pe C. Orifice — those having a constant opening and 
leakage. Non-adjustable. 

Thermostatic valves — Type A. Fig. 120 shows modifications 
of thermal control. The Webster composition expansion stem 
type, one of the earliest forms used on the mechanical vac- 
uum systems is still used on many installations. The auto- 




matic feature is the composition rubber stalk, which expands 
and contracts under change of temperature. The adjusting 
screw at the top permits the valve to be set for any condi- 
tions of temperature and pressure within the radiator. The 
water of condensation passes through a screen and comes in 
contact with the rubber stalk. The temperature of the 
water being less than that of steam the stalk contracts and 
the water is drawn through the opening A by the action of 



210 



HEATING AND VENTILATION 



the pump. As soon as the water has been removed steam 
flows around the stalk and expands it, closing the port. 
This process is continuous and automaticallj^ removes the 




^^^^y'^^^^ 



\\\ss';>^^'>^^ 



DONNELLY 



M0NA5H 




ILLINOIS 



Fig-. 121. 



water from the radiator. The screen serves ks a dirt catcher 
for the single unit. The other valves, excepting the Trane, 
have metal expansion chambers partially filled with liquids 



MECHANICAL VACUUM HEATING 211 

that vaporize at temperatures between that of the steam and 
that of the returning- condensation. In most cases the tem- 
perature approximates 200° F. The change in the vapor 
pressure within the enclosed chamber causes an expansion 
or contraction of the sides of the chamber thus closing or 
opening the valve. The expansion members of these valves 
differ in form and position. The Dunham, Monash and Illi- 
nois have single expansion chambers, the sylphon is mul- 
tiple, or accordion form, and the Haines is a bent tube. 
The expansion member of the Trane valve is composed of 
two sheet metal coil springs which in turn are made of two 
thin pieces of dissimilar metals brazed together. Since the 
coefficients of expansion of the two metals are unequal, any 
change of heat coils or uncoils the springs thus opening- or 
closing the valve. Other differences in these valves are to 
be found in the construction and location of the expansion 
member and in the style and location of the valve seat. The 
expansion member of four of the valves is in direct connec- 
tion with the radiator steam. The rest are in connection 
with the return line. Two of the valves have flat seats, 
three have conical seats and two have line contact. Four 
seats are horizontal and three are vertical. Style A valves 
are automatic, positive, noiseless and adjustable. They may 
be used under either high or low differential pressures and 
may be used on either air or condensation lines. 

Float valves — Type B. — When the differential pressure be- 
tween the radiator and the return is very small and a fitting' 
is desired that will serve merely as a separating trap to the 
radiator, a float valve or a valve actuated by the impulse 
of the water is frequently used. Fig*. 121 gives five of the 
standard forms. There are flve important features consid- 
ered in the design of these float valves, continuous air re- 
moval," intermittent water removal, freedom from steam 
leakage, convenience in cleaning and freedom from noise. 
This is a combination that is difficult to obtain. The first 
three are points of efficiency and are not easily determined 
in the operation of the average plant except under test. 
So far there are fe^v comparative data from which to draw 
conclusions. The fourth affects the attendant who has 
charge of the repair and upkeep of the plant, and the fifth 
is of vital interest to the occupant of the room. One of the 
objections frequently offered against the use of float valves 



212 HEATING AND VENTILATION 

is the occasional noisy valve. When the differential pres- 
sure between the radiator and the return is so small that it 
is alternately changing- positive and neg-ative, there is liable 
to be a chattering- of the valve, which is very annoying-. 
This is not g-eneral but frequently obtains in one or more 
valves in a system. 

Orifice — Tyjje C— In some systenis the return fitting- takes 
the form of a standard orifice which is non-adjustable and 
provides constant leakage. The use of such fitting-s is 
questionable. 

Concerning- the economy of vacuum Jieating over low pres- 
sure heating, many claims are made, some of which would be 
difficult to realize in practice. Estimates of saving rang-e 
from 10 to 40 per cent. There are no doubt increased econ- 
omies but these can not be stated in percentag-es. The two 
features of such a system that g-ive decidedly increased effi- 
ciencies are the tise of exhaust steam and thermostatic control of 
the steam admitted" to the radiator, but each of these may be 
adapted to any system and consequently should not be cred- 
ited here as economic features. On the other hand improve- 
ment in operating- conditions is so marked that a g-eneral 
statement of hig-her efficiencies is justifiable. The claim is 
sometimes made that a mechanical vacuum system using- ex- 
haust steam as a heating- medium may serve as a condenser 
to the eng-ine and improve the efficiency of the eng-ine to a 
marked deg-ree. As a matter of fact this statement will sel- 
dom be justified. The back pressure on the eng-ine "will not 
drop below atmosphere except -when the vacuum return 
valves are g-iven a constant leakag-e, in which case there 
may be g-reater loss in the plant from the latent heat of the 
wasted steam than g-ain derived from the increased mean 
effective pressure Jn the eng-ine. The one larg-e economy to 
be looked for in heating- systems lies in the use of exhaust 
steam as the heating- medium. When we consider the fact 
that exhaust steam at atmospheric pressure contains 80 to 85 
per cent, of the total heat of the live steam entering- the 
cylinder (Art. 164), that this is all wasted when exhausted 
to the atmosphere, that the condensing- engine saves only a 
small part of it and finally that the heating- system may 
save it all, there is sufficient reason to look forward to its 
increased use in combined power and heating- plants. 



CHAPTER X. 



MECHANICAL. WARM AIR HEATING AND VENTILATION 
FAN-COIL SYSTEMS. 

DESCRIPTION OF SYSTEMS AND APPARATUS 
EMPLOYED. 

120. Elements of the Fan-Coil System: — In buildings 
having- many occupants such as factories, school houses, 
theaters and auditoriums, a positive air supply to the rooms 
is usually required. To meet this condition there has heen 
developed a type of heating- and ventilating- system vari- 
ously known as the fan-coil system, mechanical warm air system 
or plenum system. This system contemplates the use of three 
distinctly vital elements: steam or hot water coils over 
which the forced air may pass and be heated, a blower or 
fan to propel the air and a proper system of ducts or pas- 
sag-e-ways to distribute this heated air to the desired loca- 
tions. Fig-s. 139 and 140 show these essentials in their rela- 
tive positions. Attachments and improved mechanisms such 
as air washers and humidifiers, automatic air and heat con- 
trol systems and brine cooling systems may be installed in 
connection with this type of heating but none of these aux- 
iliaries change in any way the necessity for the three funda- 
mentals named. 

121. Variations in the Design of Fan-Coil Systems: — 

With regard to the position of the fan, two methods of in- 
stallation are common. The first and most used is that 
shown in Fig. 122, where the fan is in the basement of the 
building and forces the air by pressure upward through the 
ducts and into the rooms. This arrangement gives the air 
within the building a pressure slightly greater than that of 
the atmosphere, causing any leakage to be outward from the 
rooms. A system so installed is a plenum system. The fan 
may, however, be placed in the attic (Fig. 123) with ducts 
leading to it from the rooms, in which case the air is pulled 
toward the fan thus causing the pressure w^ithin the build- 
ing to be slightly less than that of the atmosphere. In the 
latter case the air is supposed to enter the basement inlet. 



214 



HEATING AND VENTILATION 



pass over the coil surfaces, and when heated pass by induc- 
tion to the various rooms through the ducts. Since the 
leakag-e is inward, air from the outside readily enters at 
open windows and doors, breaking the vacuum effect of the 
fan and by-passing the heater, thus impairing the efficiency 
of the heating system. For this reason where heating is a 
vital factor, exhaust systems mithoiit the aid of pJenum systems 
are seldom installed. Combined plenum and exhaust systems 
are to be recommended wherever the expense can be justified. 




Z\ 



^^\ 



m, 






i-y 



^ 



y[ 



D 



w 



Fig. 122. 



Fig. 123. 



133. Blowers and Fans: — Many methods of moving air 
for ventilating and heating purposes have been devised. 
Some of these are positive at all times, others are dependent 
upon the existence of constant atmospheric air conditions 
and hence are a constant source of trouble. It is now a very 
generally accepted fact, that if air is to be delivered at 
definite times, in definite quantities and in definite places, it 
must be forced there by mechanical means. The recognition 
of this fact has led to a very common use of the mechan- 
ical fan or blower and its development to a fairly high 
efficiency. 



PLENUM WARM AIR HEATING 215 




Fig. 124. 
For exhaust service the fan generally used is of the 
disk or propeller blade type (Figs. 124 and 125). It is usually 
installed in the attic or near the top of the building, al- 




Fig. 125. 
though in certain cases where the plenum fan is used for 
exhaust service it may be installed in the basement. The 
plenum system uses a centrifugal fan of the paddle wheel or 
the multiple blade type (Figs. 126 and 127). The nrst with 



216 



HEATING AND VENTILATION 



plane blades, called "steel plate" fan, is the old form of fan 
wheel and is now used on mechanical draft systems in 
power plants and on the cheaper plenum heating- and venti- 
lating- plants. The second with curved blades, called "si- 
rocco," "multivane" or "conoidal" fans by the respective 
companies, is a more recent development and is especially 
adapted to plenum plants. Tests of the multiple blade fans 
show higher efficiencies than are possible with the older 
forms. In the plenum systems fans are placed between the 
air intake and the heater coils or just following the heater 
coils (See Art. 125). For theoretical discussion of fans and 
blowers see Trans. A. S. H. & V. E., Vol. XXI, p. 43; Kent's 
M. E. Pocket-Book; Marks' M. E. Handbook; and Metal 
Worker, May 2, 1908, p. 44, serial. 




Fig-. 126. 



Fig. 127. 



The motive power for fans may be of four kinds: elec- 
tric motor or steam engine (or turbine), either direct con- 
nected or belted. Which one of these drives will be the most 
appropriate in any case will depend entirely upon local con- 
ditions and the nature of the available power supply. The 
steam driven engine or turbine unit is the most economical 



PLENUM WARM AIR HEATING 



217 



since the exhaust steam from either may be used to supple- 
ment the live steam for heating- (See Arts 164 and 172). 
The electric drive is the most convenient and in places where 
fans are employed for cooling- and "where steam is carried 
at pressures too low to operate the engines, motor drives 
should be installed. Electric motors are usually belted to 
the fans. This permits the installation of motors of smaller 
sizes and higher speeds at lower initial costs. Most of the 
larger engine driven units are direct-connected. 

Fan housings are made in many different styles and of 
various materials, such as brick, wood, sheet steel or com- 
binations of these. Steel housings are the most common and 
are made to fit any requirement. Full housings are those in 
which the entire fan wheel is encased and the entire unit is 
above the floor line. Tliree-qiiarter housiiiys are those in which 
only the upper three-fourths of the fan wheel is encased, 
the completion of the air-sweep around the blades being ob- 
tained by properly forming the brick foundation upon which 
the fan is installed. Large fans are usually three-quarter 
housed, especially if they are to deliver air into underground 
ducts. Fig. 128 shows a three-quarter housing and Fig. 129 
a full housing. 




Fig. 12 



Fig. 129. 



The circular opening in the housing around the shaft is 
the inlet to the fan, the air being thrown by centrifugal 
force to the periphery and at the same time given a circular 
motion, thus leaving the fan wheel tangentially through the 
discharge opening. Fans may be obtained which will deliver 



218 



HEATING AND VENTILATION 



air at any angle with the horizontal. They may have two or 
more discharge openings (multiple discharge fans as shown 
in Fig. 129), and double side inlets, i. e., air entering the fan 
from each side of the center. Where double side inlets are 
used they are smaller than the single side inlet for the same 
sized fan. All fan casements should be well riveted and 
braced with angles and tee irons. The shaft should be fitted 
with heavy pattern, adjustable self-oiling bearings, rigidly 
fastened to the casement and properly braced. The thick- 
ness of the steel used in the casement varies according to 
the size of the fan, from No. 14 to No. 11 for sizes in gen- 
eral use. The fan wheel should be well constructed upon a 
heavy spider to protect against distortion from sudden start- 
ing and stopping. Fans should be bolted to substantial 
foundations of brick or concrete. When connecting fans to 
metal ducts where sound from the fan may be transmitted 
to the rooms, the connection between the fan and the duct 
should be made through flexible rubber cloth. 

The terms "Right Hand" and "Left Hand" refer to the position 
of the outlet relatively to a person facing the pulley or driving side 
of the fan, i. e., standing on the pulley or driving side of the fan, if 
the discharge is to your right, it is a 7'ight hand fan; if the discharge 
is to the left, it is a left hand fan. 

liia. Fresh Air Entrance to Building; 
and to Rooms: — Fresh air may enter 
through the building wall near the 
4s<<s;>Ca ground level or it may be taken from an 

elevation through a stack built for the 
purpose. In connection w^ith -washing 
systems it may be drawn from the near- 
est and most convenient source. Where 
no washing or cleaning systems are in- 
stalled care should be exercised in select- 
ing a location free from dust and other 
impurities. Where grills or shutters are 
placed in the opening, they are planned 
to obstruct the flow of the air as little 
as possible. Plain wire screens, % - to 
1-inch mesh, should always be used to 
keep out leaves, birds and small animals. 
In exposed places stationary slats or 
grills should be put in and pitched to 



AIR INTAKE. 




Pig. 130. 



PLENUM WARM AIR HEATING 



219 



keep out the rain. The amount of slope is dependent upon 

the width of the slat. In determining- the net area of such a 

grill use the perpendicular distance between the slats and 

not the vertical spacing (See Fig. 130). 

Air enters the rooms through 
registers, register faces or de- 
flectors located above the heads 
of the occupants. Registers are 
used when volumetric regula- 
tion is not provided for else- 
where in the system. Register 
faces serve no economic pur- 
pose and are put in for orna- 
mentation. Deflectors are fre- 
quently substituted for register 
faces to direct the air in deflnite 
lines about the room thus aid- 
ing uniform circulation. Where 
deflectors are used, registers 
and register faces are omitted. 
Fig. 131 shows the air inlet to 

a room with deflector attachment. 

The construction of the dead end of the warm air stack 

is important. Never finish to a square end as in Fig. 132, a. 

Always have an easy curve as in &. This may be surfaced 




Fig. 131. 



^hcfarj 




smooth with neat cement mortar over the rough bricks, but 
a better way is to have tin or light galvanized iron ends 
made to size and built in with the walls. These metal ends 
are still more efficient when fltted with sjjUtters as shown in 



220 



HEATING AND VENTILATION 



DAMPEI? CONrf^OL 



c. It is found from tests that much more air is delivered 
through a given stack for the same power expenditure 
when these are used. In the average air inlet to a room the 
lower one-third of the opening- is almost wholly ineffective. 
Where splitters are used each part 
of the opening is equally effective. 
Yemt openings are placed at the 
floor line and should be fitted with 
registers to close at night to avoid 
heat loss. Behind such registers 
there is always an accumulation of 
dust and dirt which is very unsani- 
tary. When other m^ans are pro- 
vided for closing the vents, such as 
dampers within the stacks or at 
the top of the stacks in the attic, 
registers may be omitted and the 
vent openings curved and finished 
with cement flush with the floor 
line, as in Fig. 133. This permits 
the ducts to be more easily cleaned 
Fig. 133. than where registers or faces are 

used. Automatic air control from the fan room on aU vents that 
lead to the attic is advisable. In buildings having air supplied 
to two or more floors it is frequently necessary to condense 
the stacks into the smallest space possible. Fig. 134 shows a 
common arrangement. Notice that any vertical wall space 
may serve both as a heat stack for a lower room- and a vent 
stack for an upper room. To accommodate large stacks the 
thickness of the wall is usually increased. All offsets must 
be made to fit the sizes of the standard bricks used. 




Allowable velocities for net openings are higher than 
the corresponding velocities in furnace systems (See Table 
XXIV. Register sizes are given in Table 19, Appendix. 



124. Heating Surfaces: — Heating surfaces used with 
plenum systems may be divided into two classes: pipe coil 
surface made of loops of 1- or li/4-inch wrought iron or steel 
IDipe and cast surface, made of hollow rectangular castings 
provided with numerous staggered projections to increase the 
outside surface and provide greater air and iron contact. To 
make a heater of either kind of surface, successive units are 



PLENUM WARM AIR HEATING 



221 



assembled side by side, until the requisite total area and 
depth have been obtained. The total number of square feet 
of cast or pipe coil surface exposed to the air determines the 




6 



a 



n r 





ti 



IT 
Fig. 134. 



total number of heat units given to the air per hour, while 
the depth of the heater and the spacing- of the coils control 
the final temperature of the air leaving- the heater. Data 

upon these points have 
been obtained throug-h 
exhaustive tests. Each 
must be considered in de- 
sig-ning- the heater system 
(See Arts. 136, 137, 139 
and 140). 

Pipe coils may be used 
with any steam pressure 
but cast coils should never 
be used with pressures 
exceeding- 25 pounds per 
square inch g-ag-e. All 
plenum heating- surfaces 
should be well vented 
■p. -,05 and drained. Ample al- 

lowances also should be 
made for expansion and contraction. 




222 



HEATING AND VENTILATION 




Fig. 136. 



Coil surface is of three kinds: that having- the pipes 
inserted vertically into a horizontal cast iron header which 
forms the base of the section (Fig. 135); that having the 
pipes horizontal between two vertical side headers (Fig. 
136); and that having one header vertical and one horizontal 

called the miter coil (Fig. 
137). Sections fitted with 
pipe coils may be had two, 
three or four rows of pipes 
in depth. The standard num- 
ber of rows of pipes in any one 
section is four. Sometimes 
these pipes are spaced in 
straight lines parallel with 
the w^ind and sometimes 
they are staggered. Stag- 
gered spacing increases somewhat the friction of the air 
current and the power of the fan. Heat efficiency tests of 
both straight and staggered spacings show little difference. 
Coil sections represented by Figs.' 136 and 137 have better 
drainage than those shown by Fig. 135. In the latter the 
condensation must flow against the steam or be carried over 
with it to the return. All condensation that collects in the 
supply side of the header must drain to the return side 
through one or more small holes in the division plate. This 
method of drainage is not satisfactory because the total 
area of the openings is constant and the amount of con- 
densation to be passed is vary- 
ing, thus causing a clogging 
by extra condensation or a 
short circuiting- of the steam 
to the return. The miter sec- 
tion in addition to perfect 
drainage, has perfect expan- 
sion, permitting every pipe to 
assume any position necessary 
to account for a . reasonable 
change of length without 
causing breaking stresses in 
t iiiijiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiin t the pipe threads. 

''■» I 1 Cast iron radiating surfaces for 

Fig. 137. plenum systems are cast in 




PLENUM WARM AIR HEATING 



223 



Stea-rn ■ 



units called sections, and these 
are joined top and bottom by 
nipples into larger units called 
stacks, quite similar in all re- 
spects to a direct hot water 
radiator. Stacks are assembled 
one in front of another in the 
direction of the air current thus 
forming- a heater. Fig-. 138 sho-ws 
a heater ten sections in -width 
and t-wo stacks in depth. Pro- 
vided the conditions demand it, 
the heater may be built two or 
even three stacks in heig-ht, 
thus doubling- or tripling- the 
g-ross wind area (See Art. 140). 
Cast iron heaters of the vento 
type are made in sizes shown 
by Table XXIII. It is unusual 
to assemble less than five or 
more than twenty-five sections 
to the stack. By the proper ad- 
justment of number of sections 
to the stack and of stacks to 
the heater, any requirement of 
plenum system may be met. 

Heaters are placed on either 
the suction or force side of the 
fan, usually the former in dry- 
ing or evaporating plants and the latter in heating plants. 
Because of their weight, ample and firm foundations must be 
provided, with metal surface on top of foundation to permit 
expansion movement. In most installations for heating pur- 
poses, where both tem.pered and heated air are supplied, the 
heater is raised above the floor 18 to 30 inches to permit an 
air passage and damper for tempered air. 

125. Division and Location of Coil Surface: — It is com- 
mon practice to install heaters for plenum systems in two 
parts, known as tempering coils and heating coils. The total 
heating surface is first calculated and then divided into tem- 
pering and heating coils in desired proportions. The tem- 
pering coils are placed in the air passage just inside the in- 




224 HEATING AND VENTILATION 

TABLE XXIII. 
Vento Cast-iron Heaters — Steam or Water. 



Narrow 
Sections 


Sq. Ft. per 
Section 


Height 


Width 


40 inch 


7.50 


4W. 


6% 


50 inch 


9.50 


5011 


6% 


60 inch 


11.00 


60ii 


6% 


Regular 








Sections 








30 inch 


8.00 


30 


91/8 


40 inch 


10.75 


41hV 


SVs 


50 inch 


13.50 


50§S 


91/8 


60 inch 


16.00 


6011 


91/8 


72 inch 


19.00 


72 


91/8 



take of the building- and usually contain from one-fourth to 
one-third of the total heating surface. In this way ex- 
tremely cold air is tempered before it reaches the fan thus 
insuring- good lubrication and preventing an accumulation 
of frost on the fan blades, which would seriously interfere 
with the free movement of the air. The heating coils are 
placed just beyond the fan- on the force side (See Figs. 139 
and 140). 

Com'bined plenum and gravity -in direct systems (Fig. 141) have 
been installed in which the heating coils (tempering coils 
placed as before) have been divided and used in sections at 
the base of the stacks leading to the various rooms. Such 
an arrangement does not impair the plenum system and has 
an advantage in being able to by-pass the air through the 
plenum chamber and use the sectional heaters as an indirect- 
gravity system during the night and at other times when the 
fans are not running. With the coils divided as stated and 
the same amount of surface put in the indirect-gravity coils 
as would be required in the plenum heating coils, the gravity 
system will temper the room air but will not keep the rooms 
at the same temperature as when operating with the fan, 
because of the reduced volume of the air moving and the 
corresponding drop in efficiency of the heating surface. This 
difficulty may be overcome by installing more indirect- 



PLENUM WARM AIR HEATING 



225 





ELEVATION 



Fig-. 139. Fan Room Layout with Single Ducts along 
Basement Ceiling and all Mixing Dampers at Plenum 
Chamber. 



226 



HEATING AND VKXTILATIOX 




Fig-. 140. Fan Room Layout with Double Undergrround 
Ducts and Mixing- Dampers at Base of Room Stacks. 



PLENUM WARM AIR HEATING 



227 




Fig. 141. Fan Room Layout with Heating- Coils Divided 
into Individual Room Heaters, 



228 HEATING AND VENTILATION 

gravity heating- surface. In many plants (school buildings 
and the like) a moderate temperature (50° to 60°) through- 
out the night is all that is necessary and such an arrange- 
ment of coil surface is satisfactory (See Trans. A. S. H. & 
V. E., Vol. XIV, p. 96; Vol. XVII, p. 270; Vol. XVIII, p. 370). 

In large installations where ventilation is of prime im- 
portance the ideal arrangement is the split system, i. e., ple- 
num heating coils sufficient to heat the ventilating air from 
the outside temperature to say 80°, and direct radiation 
within the rooms sufficient to keep the room air at 60° dur- 
ing the night and at times when ventilation is not needed. 
This system is especially adapted to schools (Pigs. 154 to 
156) where for sixteen hours out of the twenty-four heating 
only is required. During the eight hours when air circula- 
tion is needed the amount of ventilating air may be regu- 
lated as desired, independent of the heating. In the split 
system automatic teinperature control should be installed as 
a connecting link between the ventilating and heating sys- 
tems. The temperature of the rooms on the coldest nights 
will be, say 60°. The radiators will be in service until with 
the aid of the plenum system (started at 8 to 8:30 A. M.) 
the room air is raised to 70° when the direct radiation is 
automatically thrown out of service. The radiators continue 
automatic action in connection with the plenum system hold- 
ing the room temperatures M^ithin two degrees of fluctuation 
(generally 69° to 71°). "When the plenum system shuts 
down all radiators throw on and night conditions prevail. 

136. Single Duct Plenum System; — The duct systems 
that carry the air may be either of the single duct or double 
duct type. In both types of plants the fan delivers the air 
to a small room known as the plenum chamber. This chamber 
is divided into two parts, the upper one (hot air chamber) 
receives the air after leaving the heating coils; the lower 
one the air that has been warmed by the tempering coils. 
In the sing-le duct system (Fig. 139) a single metal duct is 
carried from the base of each vertical heat stack to this 
plenum chamber and connected to both hot and tempered 
air through a mixing- damper controlled by thermostat from 
the room supplied. Most ducts are carried along the base- 
ment ceiling and when the ceiling height is sufficient there 
is a false ceiling installed below the ducts for artistic 
effect. This system requires a complicated network of dam- 



PLENUM WARM AIR HEATING 



229 




Fig. 142. 



pers and ducts at the plenum chamber which to a certain 
degree limits its use. Fig-. 142 shows a single duct installa- 
tion applied to factories of several stories. 

127. Double Dnct Plernim System; — As the name indi- 
cates, this system (Fig. 140) runs all ducts in pairs (one 
above the other) from the plenum chamber to the base of 
each vertical room stack. The upper duct carries warm air 
from the heating coils v/hile the lower duct carries tem- 
pered air. The mixing dampers are consequently located 
at the base of the vertical room stacks. The dampers may 
be hand controlled by chain pulls from the rooms above or 
automatically controlled by thermostats. With this arrange- 
ment it is evident that the principal ducts become trunk lines 
and are composed in a minimum of space. 

Double duct systems are frequently installed as sub- 
basement systems, as compared with the single duct systems 
which have usually metal ducts along the ceiling. Such ducts 
are below the basement floor and are constructed of brick 
and cement, or of concrete, about 4 inches thick. For de- 
signs of conduits, ducts and dampers see Figs. 139, 140, 151 



230 



HEATING AND VENTILATION 




Fig-. 143. 

and 154. Fig-. 143 shows a complete steel housed plenum 
unit of fan, coils, dampers and duct connections. For shapes 
and sizes of fans see manufacturers catalogs. 

128. Air Washing and Humidifying Systems: — In con- 
nection with mechanical warm air heating and ventilating 
systems, there is often installed apparatus for washing and 
humidifying the air. In crowded city districts where the air 
is laden with dust, soot, the products of combustion and 
other harmful g-ases, its purification and moistening becomes 
a most important problem. The plenum system of heating 
and ventilating lends itself most readily to the solution of 
this problem, with the result that modern practice is tend- 
ing more each day toward the combined installation of heat- 
ing, ventilating and humidifying apparatus. 




Fig. 144. 



PLENUM WARM AIR HEATING 231 

A purifier comprises two parts, a loasher and an eliminator 
(See Fig-. 144). Tlie washer is located in the main air duct 
immediately behind the tempering coils, and provided with 
sheets or sprays of water through which the air must pass. 
Having caught the dust particles and dissolved some of the 
soluble gases from the air, the water falls to a collecting 
pan at the bottom of the spray chamber, and from there is 
again pumped through the spraying nozzles. As the water 
becomes too dirty or too warm, a fresh supply is delivered 
to the collecting pan. A small independent centrifugal 
pump is used for circulating the spray water. 



I IJ. 



!--/////y//y////y//// 





Fig. 145. Pig. 146. 

After passing through the washer, the air next encoun- 
ters the eliminator, the purpose of which is to remove the 
surplus moisture, solids and water particles remaining sus- 
pended in the air. This is accomplished by baffle plates 
(Fig. 145), which change the direction of the air many 
times in succession and cause the water particles and solids 
to impinge upon the baffle plates and fall to the drip tank. 
As the air leaves the eliminator and enters the fan it may, 
with good apparatus, be relieved of 98 per cent, of all dust 
and dirt, may be supplied with moisture to very near the 
saturation point, and in summer time under favorable con- 
ditions, may be cooled from 5 to 15 degrees lower than the 
outside atmosphere. This is due to the cooling- effect of 
vaporizing part of the water. 

A purifier designed upon different lines than that in the 
last figure is shown in Fig. 146. In this the air inakes a 



232 



HEATING AND VENTILATION 



double reverse curve and passes through four lines of spray- 
before reaching- the eliminator. 

Fig. 147 represents the Zellweger combination fan and 
purifier which has proved very satisfactory in offices and small 
schools. This is similar to the ordinary blower fan except- 
ing that the wheel is a combined filter ring 9,nd eliminator. 
Water may be circulated entirely or in part by the tan- 

CO/iTffOL 




Fig. 147. 



gential force of the water as it leaves the wheel. Air enters 
the wheel through the side opening and in passing through 
the wheel rim, which is composed of several layers of fine 
meshed wire cloth inside the curved vanes of the wheel, it 
comes in contact with the spray water from four spray 
heads. The outer edges of the blades are turned to form 
small gutters which catch the water and direct it to the 
large end of the wheel (wheel conical on surface) to the 
skimmer and collector ring for recirculation or for drainage. 
Full or three-quarter housing, single or double inlet and 
wheel diameters from 2.3 to 13 feet may be obtained. 



PLENUM WARM AIR HEATING 233 

An air washer well installed and maintained may be 
expected to remove 98 per cent, of all dust, dirt, soot, etc.; 
to lower the temperature of the air 85 per cent, of the initial 
wet bulb depression; to raise the temperature of the enter- 
ing- air from 35° to any temperature up to 60" and to add 
the necessary moisture to obtain any relative humidity up to 
75 per cent, when the rooms are 70°; and to control the rela- 
tive humidity within 5 per cent, variation when the wet bulb 
temperature of the air entering the purifier is below^ the de- 
sired dew point, all with a frictional resistance in the puri- 
fier not to exceed .2 inch water gage. 

Special air cooling plants are installed in connection 
with the plenum system of ventilation, whereby refrigerated 
brine is circulated in the regular heating coils. (See Trans. 
A. S. H. & V. E., Vol. XV, p. 252). 



CHAPTER XI. 



3IEGHANICAL WARM AIR HEATING AND VENTILATION. 
FAN-COIL SYSTEMS. 

AIR, HEATING SURFACE AND STEAM REQUIREMENT. 
PRINCIPLES OF DESIGN. 

129. Definition of Terms: — Some of the technical abbre- 
viations that are frequently used are the following: H =z 
B. t. u. heat loss per hour by heat loss formula, Hv = B. t. u. 
heat loss per hour by ventilation, H' = total B. t. u. loss = 
H + Hv, Q = cubic feet of air used per hour as a heat car- 
rier (calculated from H), Q' =. 1800 ISf = cubic feet of air 
used in obtaining- duct sizes, etc., when air for "yentilation is 
in excess of air for heating-, R = total square feet of heating- 
surface in indirect heaters, ^.s = temperature of the steam 
or water in the heaters, t zn highest temperature of' the air 
at the register (assumed the same as the temperature of the 
air upon leaving the heater), f = temperature of the air in 
the room, tv = temperature of the air at the register when 
Q' is used and t is reduced to keep^ the room from being 
overheated, to = temperature of the outside air, K = rate 
of transmission of heat through the coils, N = the number 
of persons to be provided with ventilation, Y = velocity in 
feet per minute and v = velocity in feet per second. Other 
abbreviations are explained in the text. 

130. Theoretical Considerations: — For illustrative pur- 
poses, references will be made throughout this discussion to 
a sample plenum design. Figs. 151, 152 and 153. These show 
the essential points of most plenum work and will serve as a 
basis for the applications. In any plenum design the fol- 
lowing points should be theoretically considered for each 
room: heat loss, cubic feet of air per hour needed as a heat 
carrier (this should be checked for ventilation and the 
greater value used), net area of the register in square 
inches, catalog size of the register and area and size of the 
ducts. In addition to these the following should be investi- 
gated for the entire plant: size of the main leader at the 
plenum chamber, size of the principal leader branches, square 



PLENUM WARM AIR HEATING 235 

feet of heating- surface in the coils, lineal feet of coils, 
arrangement of the coils in stacks and heaters, horse-power 
capacity and revolutions per minute of the fan including 
sizes of the inlet and the outlet of the fan, horse-power of 
the engine including the diameter and the length of stroke, 
and pounds of steam condensed per hour in the coils. 

Fresh air is taken into the building at the assumed low- 
est temperature, io° , is carried over heated coils and raised 
to t° (in certain cases to ti°), is propelled by fans through 
ducts to the rooms and then exhausted through vent ducts 
to the outside air. It is the object of this section to so dis- 
cuss this cycle that the principles may be applied to gen- 
eral problems. 

131. Heat Loss and Cubic Feet of Air per Hour: — It is 

assumed in these calculations that the circulating air is all 
taken from the outside and thrown away after being used. 
Many installations have arrangements for returning part or 
all of the air to the coils and reheating it as an economic 
method of operation but this should not be taken into con- 
sideration in obtaining the sizes of the heaters. It is best 
to design the plant with the understanding that all the air 
is to be thrown away. It w^ill then be large enough for any 
service that it may be expected to handle. Having found H 
by some acceptable equation (See Art. 39), the total heat 
loss is 

iQ or Q') if — In) 

H' =: H -\ (See also Arts. 42 and 50). (61) 

55 

Assuming to = 0° as the lowest temperature at which fresh 
air will be admitted (any temperature lower than this would 
call for recirculated air) this equation reduces to H' = H -\- 
1.27 (Q or Q'). To determine whether or Q' will be used 
find Q from H, Equation 33, and compare with Q', taking the 
larger value. If this is to be a system of plenum heating 
only, let t = 140°, t' = 70° and to = 0°, then 

55 // // H 

N = = = approximately (62) 

1800 (t — f) 2290 2300 

and since f — f = t' — to, H' = 2 H, that is to say, the heat 
given off from the air in dropping from the register tem- 
perature 140° to the room temperature 70°, goes to the radi- 
ation and leakage losses //, while that given off between the 



236 HEATING AND VENTILATION 

inside temperature 70° and the outside temperature 0°, is 
charged up to ventilation losses Hv. Since these values are 
equal, H' = S + Hv = 2 H. 

Application. — Referring- to Fig-. 152, room 15, the calcu- 
lated heat loss for this room, with V = 70° and to = 0°, is 
70224 B. t. u. per hour; also, if * = 140°, Q = 54775 cubic feet 
per hour. Applying Equation 61, the total heat loss is 
140448 B. t. u. per hour. With 54775 cubic feet of air sent 
to the room per hour, this provides good ventilation for 
thirty persons. Suppose, however, that fifty persons are to 
be provided for; this requires 50 X 1800 = 90000 cubic feet 
of air per hour. With this increased number of people in 
the room, the total heat loss is 

90000 (70 — 0) 

H' = 70224 H • = 184864 B. t. u. 

55 

Find H' when N = 50 and to = — 10°. 

132. Temperature of the Bnterin^ Air at the Reg;i!ster: — 

In plenum heating the registers are placed higher in the 
wall and the velocity of the air is greater than in furnace 
work. Suppose for this work the maximum temperature t =. 
140° excepting where an extra amount of air is required for 
ventilation purposes, in which case the temperature must 
necessarily drop below 140° in order that the room will not 
be overheated, then 

55 H 

t = r ^ (63) 

Q' 

Application 1. Referring to room 15 (compare -with Art. 
52) assuming the heat loss to have been estimated with ven- 
tilating air supplied sufficient for 50 persons, 90000 cubic 
feet per hour, the temperature of the air at the register is 

55 H 

t = 10 -] = 113° 

90000 

Find t when N = iO and to = 20°. 

Application 2. — Referring to room 12 and assuming 200 
persons in the room with 360000 cubic feet of air per hour, 
the temperature of the entering air will be 89°. 

These applications do not take into account the heat 
given off by the audience, which would permit the reduction 



PLENUM WARM AIR HEATING 



237 



of the entering- air somewhat below the temperatures stated 
(See Art. 44). 

The register air temperature is usually taken the same 
or slightly less than the temperature of the air upon leav- 
ing the coils. If this room were to be the only one heated, 
the coils would be figured for a final temperature of the air 
at 113°, but other rooms may have air entering at higher 
temperatures, consequently the temperature * upon leaving 
the coils should be that of the highest t at the registers. 

133. Cubic Feet of Air Needed per Hour: — The amount 
of air needed per hour as a heat carrier (compare with Art. 
50) is 

55 // H 

1.27 
1800 N. 



where t = 140 and f =z 70, Q 



t — t 
If extra air is needed for ventilation 



134. Air A^elocities, V, in the Plenum System: — Table 
XXIV gives the velocities in feet per minute that have been 
found to give good satisfaction in connection with blower 
systems. 

TABLE XXIV. 
Air Velocities in Plenum Systems. 





Fresh 

air 
intake 


Over 
coils 


Main 
duet 
near 
fan 


Smaller 

branch 

ducts 


Stacks 


Reg'rs 
or other 

open'gs 


Offices, 
schools, etc. 


^ o 

li 


^11 

sP 

1—1 ^ _r 

ill 


1200 to 

180O 
say 1500 


80Oto 
1200 

say 900 


500 to 
700 

sayOOO 


300 to 

400 
saySOO 


Auditoriums, 
churches, etc. 


1500 to 

20OO 
say 1800 


lOOOto 

1500 
say 1200 


600to 

80O 
say 70O 


40Oto 

600 
say 400 


Shops and 
factories 


1500 to 

3O0O 
say 2000 


lOOOto 

20OO 
say 1500 


600 to 

1000 

saySOO 


400 to 

800 
say 500 



135. Cross Sectional Area of Registers, Ducts, etc.: — 

With the above velocities in feet per minute, the square 
inches of net opening at any part of the circulating system 
may be obtained by direct substitution in the general equa- 
tion 

144 (QovQ') 

= 2.4 

60F V 



A = (Q or Q') X 



(64) 



238 HEATING AND VENTILATION 

The calculated main duct sizes refer to the warm air 
duct. The cold air duct in a double duct system need not 
be so large because on M^arm days when only tempered air 
is needed, the steam may be turned off from one or more of 
the heaters, permitting- the warm air duct to furnish what 
otherwise would be required from the cold air duct. On 
account of this flexibility in the warm air system it seems 
necessary to make the cold air duct only one-half the cross 
sectional area of the warm air duct. For convenience of 
installation it would be well to make the former the same 
width as the latter and one-half as deep, unless by so doing- 
the cold air duct becomes too shallow. 

Application. — Assuming 2000000 cubic feet of air passing- 
through the main heat duct at A, Fig. 151, per hour at the 
velocity of 1800 feet per minute, the duct is approximately 
20 square feet in cross-section, or 2 V^ by 8 feet. The two 
main branches at B carry 800000 cubic feet per hour each at 
the same velocity and are 7.4 square feet in area, or 2 by 4 
feet. The same branches of C carry 400000 cubic feet per 
hour each at a velocity of 1500 feet per minute and are 4.4 
square feet in area, or 2 by 2^^ feet, and branch D carries 
300000 cubic feet at a velocity of 1200 feet per minute and is 
IVa by 2% feet. 

The stack si^e.s are first calculated for a velocity of 600 
feet per minute and then made to fit the laying of the brick 
work such that the velocities are 600 feet per minute or less. 
The net register is calculated for an air velocity of 300 feet 
per minute and the gross registers are taken 1 to 1.5 times 
the net area (the smaller value is used with splitters and 
diffusers). 

136. Final Aii* Temiieratiires: — Since the amount of 
heat transmitted is directly proportional to the difference of 
temperature between the two sides of tRe metal, the first 
coils in a heater are the most efficient, this efficiency drop- 
ping off rapidly as the air becomes heated in passing over 
the coils. Final temperatures for different numbers of coil 
sections in banks have been found by experiment and may 
be taken from Table XXV (See also Table XXIX). 



PLENUM WARM AIR HEATING 



239 



TABLE XXV. 

Temperatures of Air upon Leaving- Coils, Steam 227' 

Air entering- at 0°. 





No. of 
roAvs 


Velocities of air through coils in F 


P. M. 


Sections 


800 


1000 


120O 


1500 


I 


4 


42 


33 


28 


23 


2 


8 


71 


62 


56 


52 


3 


1-2 


96 


87 


SO 


75 


4 


16 


119 


108 


101 


93 


5 


20 


136 


12.5 


116 


108 


6 


24 


1.53 


140 


131 


120 


7 


28 


169 


155 


143 


131 


8 


32 


183 


166 


154 


141 



These temperatures may be increased about 10 per cent, 
for 20 pounds g-ag-e pressure. 

Table XXVI sho-ws similar results quoted for the Vento 
cast iron heaters. 

TABLE XXVI. 

Temperature of Air upon Leaving- Vento Coils, Steam 227°. 

Reg-ular and Narrow Sections, 5 Inch Centers. 





Velocities of air through coi 


s in F. P. M. 




No. of 
stacks 

in 
depth 












80O 


lOOO 


1200 


1400 


Ent. Temp. 


0° 


-10° 


-20° 


0° 


-10° 


-20° 


0° 


-10° 


-20° 


0° 


-100 


-20" 


1 


Reg. 

Xar. 


.38 






35 






■Py] 












2 


Reg. 


68 


62 


55 


6-2 


56 


49 


58 


51 


44 


54 


47 


40 




Nar. _ _ 


51 


43 


36 


46 


38 


31 


43 


35 




40 


3-' 




3 


Reg. 


93 


87 


82 


86 


80 


75 


81 


75 


69 


76 


7ti 


64 




Nar. 


70 


64 


58 


65 


58 


,52 


61 


54 


47 


57 


50 


43 


4 


Reg. 


113 


108 


103 


106' 


101 


96 


100 


95 


90 


95 


89 


84 




Nar. 


88 


83 


77 


82 


76 


70 


77 


70 


64 


72 


65 


59 


.5 


Reg. 


129 


126 


122 


122 


118 


114 


n.^ 


111 


107 


1(19 


105 


100 




Nar. 


103 


98 


93 


96 


91 


86 


90 


&4 


79 


85 


79 


74 


6 


Reg. 


143 


140 


137 


13.5 


1.32 


129 


129 


125 


121 


1-23 


119 


115 




Nar. 


115 


111 


107 


108 


103 


99 


lf>2 


97 


92 


97 


92 


87 


7 


Reg. 


154 


1.52 


1.50 


147 


144 


141 


140 


1.37 


134 


1.35 


131 


128 




Nar. 


127 


124 


120 


120 


116 


112 


114 


109 


105 


108 


103 


99 



240 HEATING AND VENTILATION 

137. Square Feet of Heating Surface, R, in the Coils: — 

To determine the number of square feet of heating- surface 
in the coils of an indirect heater, the following equation may 
be used: 

H' 

R = (65) 



/ t+to\ 

" {'■ — —) 



Rule. — To find the square feet of coil surface in an indirect 
heater, divide the total heat loss from the building in B. t. u. per 
hour by the rate of transmission multiplied by the difference between 
the inside and the average outside temperatures of the coils. 

Equation 65 presupposes a uniform rise in the tempera- 
ture of the air as it passes over the coils, i. e., if the air is 
heated from 0° to 140° in passing- over a heater 24 pipe rows 
deep, at the sixth row the temperature would be 35°, at the 
twelfth row 70°, and at the eighteenth row 105°. It is found 
that this is not the case but that the rise is more rapid in 
passing over the first part of the heater, gradually falling 
off to the end of the heater according to the logarithmic 
curve. The mean temperature difference between the inside 
and the outside of the heater instead of coming from an 
arithmetical mean as given within the brackets, Equation 



the the he 

r 

(Oa — Ob \ 

lOge (Oa/Gft) / 



65, is Qm = (Qa — Qb) -^ loge I I and the total number 

of square feet of radiation in the the heater is 

H' 
R = : (66) 



lOge (ea/G6) 

where Qm = mean temperature difference, Qa =r temperature 
difference at the entering end and 0& = temperature differ- 
ence at the leaving end. For full discussion of Equation 66 
see Elements of Heat Power Engineering, Hirshfeld and 
Barnard, Chapter XXXV. Equations 65 and 66 give approx- 
imately the same results, as shown by Equations 67 and 68. 
The first is more easily applied and is recommended for 
ordinary heater calculations. These equations are rational 
and the terms indicated are readily apparent excepting per- 
haps the value K. Various experimenters have done exten- 
sive work toward establishing this and a few of their re- 
sults will be briefly summarized. 



PLENUM WARM AIR HEATING 



241 



Prof. Carpenter quotes extensively from experiments 
with coil heaters in blower systems and summarizes in the 
equation ET = 2 + 1.3 Vv where v is the average velocity of 
air over the coils in feet per second. With coil velocities in 
common use, 800 to 1400 feet per minute, this equation gives 
K from 7 to 8.5, which are very conservative and safe values. 

Mr. F. R. Still gives the following equation for the total 
B. t. u. transmitted per square foot per hour, between the 
temperature of the steam and that of the entering air, total 
B. t. u. transmitted. = c Vv' (ts — to), (Table XXVIII), in which 
c is velocity in feet per second and c is a constant which 
varies with the number of sections as shown in Table XXVII. 

TABLE XXVII. 
Values of c. 



1 section 4 rows of pipe 

2 sections S rows of pipe 

3 sections 12 ro^vs of pipe 

4 sections 16 rows of pipe. 

5 sections 20 rows of pipe 

6 sections 24 rows of pipe 

7 sections 28 rows of pipe 

8 sections .32 rows of pipe 

9 sections 36 rows of pipe 
LO sections 40 rows of pipe. 




From the above values of c, Table XXVIII has been com- 
piled, assuming ts = 227, to = and c = safe factor. 



TABLE XXVIII. 



Velocity 
of air 
in feet 

per niin . 


Total transmission in B. 

ts = 227 


t. u. per sq. ft. per hour. 

; to = 0. 


Rows of pipe deep 


4 


8 


12 


16 


20 


24 


28 


32 


800 
1000 
1200 
1400 


2840 
3200 
3500 
3783 


2470 
2790 
3040 
3290 


2164 
2440 
2670 

2884 


1920 
2170 
2360 
2555 


1750 
1900 
2150 
2325 


1606 
1810 
1980 
2138 


14.50 
1670 
-1825 
1974 


1360 
1.535 
1678 
1809 



:42 



HEATING AND VENTILATION 



Since the values g-iven in Table XXVIII are the total 
B. t. u. transmitted per square foot per hour for different 

t + 



settings = o\/v (tn 



to) 



/ t + to\ 



is found to vary 



between 10.5 and 15 with an average of approximately 12. 

Table XXIX by Mr. C. L. Hubbard shows efficiencies that 
are less than those just considered. These agree more nearly 
with average practice, 

TABLE XXIX. 

Efficiencies of Forced Blast Pipe Heaters, and Temperatures 

of Air Delivered. 

Velocity of air over coils at 800 feet per minute. 



Rows 

of pipe 

deep 


Temp, to which the air 
will be raised from zero 


Efficiency of the heating surface 
in B. t. u. per sq. ft. per hr. 


Steam pressure m heater 


Steam pressure in heater 


lb. 


20 lb. 


60 lb. 


5 lb. 


20 lb. 


60 lb. 


4 


30 


35 


45 


1600 


1800 


2000 


6 


50 


55 


65 


160O ■ 


1800 


2O00 


8 


• 65 


70 


85 


1500 


1650 


1&50 


10 


80 


90 


105 


150O 


1650 


1850 


12 


95 


105 


125 


1500 


1650 


1850 


14 


105 


120 


140 


1400 


1500 


1700 


16 


120 


130 


150' 


1400 


1500 


1700 


18 


130 


140 


160 


1300 


1400 


1600 


20 


140 


150 


170 


1300' 


1400 


1600^ 



For a velocity of 1000 feet per minute multiply the 
temperatures given in the table by 0.9 and the efficiencies 
by 1.1. 

Perhaps the most extensive work along this line has 
been done by Messrs. Willis H. Carrier and F. L. Busey. For 
details see Trans. A. S. H. & V. E., Heat Transmission with 
Indirect Radiation Vol. XVIII, p. 172. From these experi- 
ments K varied from 9 to 13 for velocities from 800 to 1400 
feet per minute. 

When estimating plenum heating surface it is well to 
remember that after a coil has been in service for a time it 



PLENUM WARM AIR HEATING 243 

becomes somewhat less efficient than while clean and new, 
also that even though the very best arrangements for air 
rem.oval are provided, these often fail or work with lessened 
efficiency. In general, even though transmission tests show 
rates of transmission as high as 12 or 13 it is much safer to 
take a lower value for average conditions. Assuming for 
illustration K = 8.5 and Y = 1000 as the best values to use; 
also ts = 227 (5 pounds gage pressure), t — 140 and to = 0, 
Equations 65 and 66 become 

IF H' 

R = — — — — = (67) 

140 + \ 1335 
8.5 I 227 I 



( 22' 



R z= = ■ (68) 

8.5 (227 — 87) 1240 



loge227/87 

Note. — At the assumed rate of transmission, 8.5, each 
square foot of heating surface is equal to 5 square feet of 
direct radiation. This is due to the increased velocity of air 
over the radiating surface. 

Cast iron heaters are being increasingly used for low pres- 
sure indirect heating, replacing pipe coil heaters. The effi- 
ciency of these heaters is, according to tests, about the same 
as that of the pipe coil heaters and hence Equations 65 and 
66 will apply to both pipe and cast heaters. For more com- 
plete data on efficiencies and final temperatures than given 
in Table XXVI see American Radiator Co.'s Engineers' Data, 
Vento Heaters. 

Application 1. Where heating only is considered. — Referring 
to Table XXXV, let H for the entire building (to = 0°) = 
1483251 and t = 140. Then from Art. 133, Q = 1156935; by 
Equation 61, 77' = 2966502; and Equation 67, the coil sur- 
face is 

2966502 

R = = 2222 sq. ft. 

140 + \ 



!.5 I 22' 



With three lineal feet of 1-inch pipe per square foot of sur- 
face we have 6666 lineal feet of coils in the heater. 

Application 2. Where heating and ventilation are combined. — 
Assume 1100 people in the building on a zero day and Q' = 



244 HEATING AND VENTILATION 

2000000. Then H' = 1483251 + 1.27 X 2000000 = 4023251, 
with equal distribution of air, t = 111, and 

4023251 

R r= = 2758 sq. ft. = 8274 lin. ft. coils. 

Ill + 
8.5 " 



I 22^ 



Application 3. Where heating and ventilation are separate. 

Split system. — With the same number of people in the building 

as given in Application 2, the heat loss H may be supplied by 

direct radiation and Hv by fan coils. In this case 

2540000 

Rv = = 1597 sq. ft. = 4791 lin. ft. coils. 

/ 80 + \ 
S.5(227 —) 

Final temperature 80° (F = 1200) gives three sections of 
regular vento (12 rows of coils) at 0° outside (See Table 
XXVI). This gives opportunity of reducing the direct radi- 
ation to give t = 60° (See also Art. 140). In applying Equa- 
tion 65, t is usually considered 140°. Conditions may exist, 
however, when this should change. For illustration, suppose 
that in a certain building most of the rooms are to be venti- 
lated and that these rooms will have large amount of air 
delivered at low temperatures (Application 2). In such a 
case it may be economy to raise the air for all rooms to the 
lower temperature and supply more air to those rooms that 
would otherwise be heated with air at 140°, than to put in a 
heater large enough to heat all the air to 140° and then 
dilute "With large amount of cold air to lower the tempera- 
ture. Again, suppose that a school building contains, in 
addition to the. regular class rooms, laboratories, etc., and 
auditorium and gymnasium, the two together requiring an 
amount of air sufficient to justify a separate fan system (a 
condition which frequently exists). It would be economy 
to separate the heating system for these rooms from the 
rest of the building because of the comparatively short time 
the rooms are in use. When not in use either fan unit may 
be shut down without interfering with the other unit, thus 
approaching a higher operating efficiency. 

138. Approximate Rules for Plenum Heating Surfaces: — 

The following approximate rules are sometimes used in 
checking up heating surface in the coils. These should be 
used with caution. 



PLENUM WARM AIR HEATING 245 

Rule 1. '^ Allow one lineal foot of 1-inch pipe for each, 65 to 
125 cubic feet of room space, 65 for office buildings, schools, etc., and 
125 for shops and laboratories." Since this building- (Fig-. 151) 
has approximately 500000 cubic feet of room space, it gives 
7700 lineal feet of 1-inch pipe in the heater. 

Rule 2. — ''Allow 200 lineal feet of 1-inch pipe for each 1000 
cubic feet of air per minute at a velocity of 1500 feet per minute." 
Applying- to the above building when the air moves over the 
coils at 1000 feet per minute, the heated surface is only 
about four-fifths as valuable and would require 250 lineal 
feet per each 1000 cubic feet of air per minute. This gives 
8333 lineal feet of coils. 

139. Arrangeiuent of Coils in Pipe Heaters: — Coil sec- 
tions are arranged in two, three and four rows of pipes per 
section. Unless special reference is made to this point, the 
latter value is understood. Having found R for the heater, 
obtain fl-om the temperature tables the number of pipe rows 
or sections deep the heater will need to be to produce the 
desired t° . Next, find the net wind area across the coils by 
dividing the total air moved by the assumed velocity of the 
coils. From the net wind area find the g-ross cross sectional 
area of the heater by the relation commonly used by manu- 
facturers — 

Gross wind area — 2.5 times net wind area. 
From the gross area the size of the heater may be selected. 

Application 1. — In Art. 137 let R = 2222, Q = 1156935, 
V = 1000 (deep heater) and * = 140. From Table XXV the 
heater will require 24 rows of coils in depth to g-ive the re- 
quired temperature. The net area will be 1156935 -4- (60 X 
1000) = 19.3 sq. ft., the gross area will be 2.5 X 19.3 = 48.25 
sq. ft. and the heater size will probably be selected 6 ft. x 
8 ft. Check for R by second method, following- Application 3. 

Application 2.— Let R = 2758, Q' - 2000000, Y = 1000 
(deep heater) and t =z 111, Find the heater 16 + say 18 
rows deep; net area = 33.3 sq. ft.; gross area = 83.3 sq. ft.; 
and size of heater = 9 ft. x 9 ft. or 2 divisions each 6 ft. x 
7 ft. Check for R as in Application 1. 

Application 3. — Let R = 1597, Q' = 2000000, V = 1200 
(shallow heater) and t = 80. Find the heater 12 rows deep; 
net area = 27.8 sq. ft.; gross area = 69.5 sq. ft.; and size of 
heater 8 ft. x 8.75 ft. 



246 HEATING AND VENTILATION 

A second method of obtaining pipe coil heater sizes is as 
follows: having- found R, obtain the square feet of heating 
surface in any one row of coils across the heater by dividing 
R by the number of rows in depth (in the applications, 24, 
18 and 12). Then from the usual relations existing between 
net area, gross area and heating surface per row obtain the 
size of the heater. Let the net area between the tubes, N. A., 
the space occupied by the tubes, T. A., and the gross cross 
sectional wind area through the tube, O. W. A., be respectively 

Q or Q' Q or Q' Q or Q' 

2V. A. = ; T. A. = ; and O. W. A. = (69) 

60 y 40 y 24 7 

Since the cross sectional space T. A. occupied by the tubes 
is to the coil surface per row as 1 : 3.1416, the total coil sur- 
face in one row of tubes is 

3.1416 (Q orQ') (Q or Q') 
7?i = = .08 • 

40 y y . 

Reduced to the basis of the net area, N. A., we have 

i?i = 4.8 times iV. A. (70) 

For illustration, when substitution is made in the three 
applications just cited we have: first, R (per row) = 92.6, 
N. A. = 92.6 ~ 4.8 = 19.3, G. A. = 2.5 X 19.3 = 48.25 and the 
size of the heater is 6 ft. x 8 ft.; second, R (per row) = 153, 
N. A. = 32, G. A. = 80 and the size of the heater is 9 f t. x 9 
ft.; third, R (per row) = 133, N. A. = 28, G. A. = 70 and the 
size of the heater is 8 ft. x 8.75 ft. 

Slight variations occur in checking between the two 
methods because of the difficulty in selecting the exact num- 
ber of rows of coils to fit the final temperatures. Either of 
the two methods as shown above for determining the size of 
the coil heater will give good practical results. 

Assembled sections of pipe coil heaters are supplied by 
manufacturers from the smallest size of 3 ft. x 3 ft., to the 
largest size of 10 ft. x 10 ft., these dimensions being those of 
the gross cross sectional area, and not overall dimensions. 
Between the two limits, both height and breadth usually 
vary by 6 inch increments. For exact sizes, consult dimen- 
sion tables in manufacturers' catalogs. 

140. Arrangement of Sections and Stacks in Vento Cast 
Iron Heaters: — Referring to Applications 1, 2 and 3, Art. 139, 
find the number of stacks deep, the number of stacks high. 



PLENUM WARM AIR HEATING 247 

the number of sections to the stack and the size of the 
heater as compared with each application in coil heaters. 

Application 1. — R = 2222 and A'. A. = 19.3. From Table 
XXVI the number of stacks deep (regular, t = 140 and to = 
0) = 6. From Table 53, Appendix, either of the following' 
arrangements will give the required N. A: (a) one stack 
high, 60 in. section, 21 sections wide; size of heater 105 in. 
wide X 60 in. high x 55 in. deep. Check i? = 336 X 6 = 2016 
sq. ft.; (b) a 40 in. stack above a 50 in. stack, 14 sections 
wide; size of heater 70 in. x 90 in. x 55 in. Check R = (189 + 
150.5) X 6 = 2037 sq. ft.; (c) a 40 in. stack above a 40 in. 
stack, 16 sections wide; size of heater 80 in. x 80 in. x 55 in. 
Check R = 2 X 112 X Q = 2064 sq. ft. 

Application 2. — R = 2758 and A'. A. = 33.3. From the 
same tables (regular, t = 111 and to = 0) the number of 
stacks deep = 5 and the following arrangements will give 
the required X. A.: (a) a 60 in. stack above a 60 in. stack, 
18 sections wide; size of heater 90 in. x 120 in. x 46 in. Check 
7? = 2 X 288 X 5 = 2880 sq. ft.; (b) a 40 in. stack above a 
60 in. stack, 21 sections wide; size of heater 105 in. x 100 in. x 
46 in. Check A' =: 2808 sq. ft.; (c) a 40 in. stack above a 50 
in. stack, 23 sections wide; size of heater 115 in. x 90 in. x 
37 in. Check R = 2789 sq. ft. 

ApPLicAtioN 3. — R = 1597 and X. A. = 27.8. Regular sec- 
tions, t = SO and to = 0, find number of stacks deep = 3 and 
the following arrangements of heaters: (a) a 50 in. stack 
above a 60 in. stack, 17 sections wide; size of heater 85 in. x 
110 in. X 28 in. Check R = 1505 sq. ft.; (b) a 40 in. stack 
above a 60 in. stack, 19 sections wide; size of heater 95 in. x 
100 in. X 28 in. Check R = 1525 sq. ft.; (c) a 40 in. stack 
above a 50 in. stack, 21 sections wide; size of heater 105 in. x 
90 in. X 28 in. Check R = 1527 sq. ft. 

Other arrangements than the above may be made to suit 
the space set aside for the heater in the building plan. It 
will be noticed that the vento coils as taken from the tables 
check somewhat below the calculated R. Where space will 
permit add enough sections to the width of the heater to 
keep the total surface up to the calculated R and permit the 
velocity of the air over the coils to drop correspondingly. 

141. L.se of Hot Water in Indirect Coils: — In most cases 
low pressure steam is used as a heating medium in indirect 
heaters. It is possible to use hot water where a good supply 



248 HEATING AND VENTILATION 

is available. In such an arrangement the coils will be cal- 
culated from Equation 65, using- all values the same as for 
steam excepting ts, which will be replaced by the average 
temperature of the water. The piping connections and the 
arrangement of the coils will follow the same general sug- 
gestions as already stated for direct heating. 

143. Pounds of Steam Condensed per Square Foot of 
Heating Surface per Hour: — From Art. 137 the number of 
pounds of condensation per hour per square foot of surface 
in the coils is 



(71) 



R X heat given off per pound of condensation 

Application. — Let R = 2758 and H' = 4023251; also let 1 

pound of dry steam at 5 pounds gage in condensing to water 

at 212° give off 1156 — 180 = 976 B. t. u. Then 

4023251 

1.5 pounds. 



2758 X 976 

This amount is an average of all the coils. The first and 
last sections in any bank may vary above or below this 
amount 33 per cent. The first coils will condense as much 
as 2 pounds of steam per square foot of surface per hour 
under heavy service. 

143. Pounds of Dry Steam Needed in Excess of the Ex- 
haust Steam Given Off from the Engine;- — In all steam driven 
plenum systems it is economy to use the exhaust steam from 
the power unit as a partial supply for the coils. Let the 
heating value of the exhaust steam from the engine be 85 
per cent, of that of good dry steam (See Arts. 164 and 172); 
also let the engine use 40 pounds of dry steam per horse- 
power hour in driving the fan. From Art. 153 the engine 
will use 40 X 13.7 = 548 pounds of steam per hour and the 
heating value will be 976 X .85 = 830 B. t. u. per pound or 
830 X 548 =454840 B. t. u. total per hour. Then 4023251' — 
454840 = 3568411 B. t. u. and 3568411 -f- 976 = 3657 pounds 
of steam. The boiler will then supply to the engine and 
coils 3657 -f 548 = 4205 pounds of steam total and ^will rep- 
resent 4205 -i- 30 = 140 boiler horse-power. 



CHAPTER XII. 



MECHANICAL, WARM AIR HEATING AND 
VENTILATION. PAN-COIL SYSTEMS. 

PRINCIPLES OF THE DESIGN, CONTINUED. 
FANS AND FAN DRIVES. 

144. Theoretical Air Velocity: — The theoretical velocity 
of air flowing' from any pressure pa to any pressure pi, is 
obtained from the general equation v —- V2gh, where v is 
given in feet per second, g = 32.16 and h = head in feet pro- 
ducing flow. The latter value may be easily changed from 
feet of head to pounds pressure and vice versa. 

When exhausting air from any enclosed space into 
another space containing air at a less density, the force 
which causes movement of the air is pa — pb = px. Pressures 
may be taken by any standard type of pressure gage. These 
show pressures above the atmosphere. "When exhausting 
from any container into the atmosphere, pb = o and pa = px. 
The fact that a difference of pressure exists between two 
points in air transmission indicates that there are two actual 
columns (or equivalent as in Fig. 10) of air at different den- 
sities connected and producing motion, or that by mechanical 
means a pressure difference is created which may be re- 
duced to an eqiiivalent head Ji by dividing the pressure head 
by the density of the air. Thus 

pressure difference pa — pb 



density d 

Let Pa — Pb ^= Px = ounces of pressure per square inch of 
area producing velocity of the air; also, let g = acceleration 
due to gravity = 32.16 and d = density (weight of one cubic 
foot) of dry air' at 60° and at atmospheric pressure (Table 
7, Appendix). Substituting in the general equation 



-i 



64.32 X liipx 

= 87 Vpx (72) 



.0764 X 16 



250 HEATING AND VENTILATION 

Since the pressure producing- flow is usually measured 
in inches of water, /(»•, the above may be changed to read in 
equivalent heiglit of water column by 

weight of water per cu. fi. at given temp. X /' •'• 

//, = (73) 

weight of air at given temperature X 12 

Applying this to dry air at G0° and water at the same tem- 
perature (Tables 7 and 9, Appendix, also Art. 29), 

G2.37/(,r 
h = • = 68 Ji,r 



12 X .0764 
which when substituted in the general equation givet 



V = \/64.32 X 68/?,r = 66.2 \/Ji,c (74) 

Equation 73 between the temperatures of 50° and 70" 
gives results varying between r rr 65.5 Vhw for 50° and v — 
66.5 VJiw for 70°. Taking the average value 

V - 66 \/lu7 (75) 

Stated as a rule for approximate calculations tlic theoretical 
velocity of air, when measured hy a water column gage that meas- 
ures in inches of water, equals sixty-six times the square root of the 
height of the column in inches. 

For calculations requiring greater accuracy, Equations 72 
and 74 should take into account the density of the air and 
its drop in temperature. First, considering only density, let 
the pressure of one atmosphere at sea level be 29.92 inches 
of mercury (14.7 pounds = 235 ounces per square inch area). 
Since the density is proportional to the absolute pressure, 
the temperature remaining constant, we have from Equation 
72 with air exhausting into the atmosphere 

/ 64.32 X 144 p.r / ^j- 

r = A = 1336 A (76) 

^ 235 + ihv ^ 235 +p,- 

.0764 X 16 X 

235 

Also from the relation existing between Equations 72 and 74, 
Equation 76 reduces to 



4 



133GA/ (77) 

407 + hw 



PLENUM WARM AIR HEATING 



251 



Second, considering both density and temperature, Equations 
76 and 77 become 



1336 



// 460 + f \ p. 

^ \ 520 / 235 + i)j 

1/ 460 +# \ 



(78) 



(79) 



407 + hw 

To facilitate calculation, the second columns in Tables 
XXX and XXXI have been compiled from Equations 76 and 77 
respectively, and the second column in Table XXXII has been 
compiled for different temperatures on the basis of 60° from 
that portion of Equations 78 and 79 included within the paren- 



Column 



TABLE XXX. 
figured from Equation 76. 



s 




1 


Vol. of air in 




G 


Velocity of dry air at 60° es- 


cu. ft. which 


H. P. required 


§.d 


caping- into the atmosphere 


may be dis- 


to move the 
g-iven vol. ol 
air under the 


through any 


shaped orifice 


charged i n 1 


'7. ^ 


m any pipe or reservoir m 


min. through 


53 !-. 


which a given pressure is 


an orifice hav- 


given conditions 


^ft 


maintained. 




ing an effective 


of discharge. 








area of dis- 
charge of 1 sq. 


(Col. 3 X Col. 1) 


Ph 










Ft. per see. 


Ft. per min. 


in. 

Col. 3 -- 144 


16 X 330OO 


Vs 


30.80 


1848.00 


12.83 


0.00044 


V4 


43.56 


2613.60 


18.15 


0.00124 


% 


53.27 


3196.20 


22.19 


0.00227 


V2 


61.56 


3693.60 


25.65 


0.00349 


% 


68.79 


4127.40 


28.66 


O.0X>489 


% 


75.35 


4521.00 


31.47 


0.00642 


% 


81.37 


4882.20 


33.90 


O.0O8O9 


1 


86.97 


5218.20 


36.24 


0.00988 


IVs 


92.18 


5530.80 


38.41 


0.01178 


m 


97.18 


5830.80 


40.49 


0.01380 


1% 


101.90 


6114.00 


42.46 


0. 01592 


1% 


106.40 


6384.00 


44.33 


0.01814 


1% 


110.82 


6649.20 


46.11 


O.02O46 


1% 


114.86 


6891.60 


47.86 


0.02284 


IVs 


118.85 


7131.00 


49.52 


0.02533 


2 


122.47 


7348.20 


51.03 


0.02787 



thesis. From these three columns of tabulations the theo- 
retical velocity of air under any pressure and temperature 
change may be obtained without using the equations, by 
multiplying the velocities found in Tables XXX and XXXI 
by the factor for temperature correction given in Table 
XXXII. Other points of information concerning velocities. 



25L' 



HEATING AND VENTILATION 



pressures, weights and horse-powers in moving- air may be 
obtained by multiplying by the factors as given in the re- 
spective columns. 

TABLE XXXI. 
Column 2 figured from Equation 77. 





Velocity 


of dry air at 60° escaping into the atmosphere 


Pressure 


through 


any shaped orifice in any pipe or reservoir in which 


head in 


a given pressure is maintained. 


inches of 












water 


Peet per second 


Feet per minute 


.1 




20.94 


1256.40 


.2 




29.67 


1780.20 


.3 




36.25 


2175.60 


.4 




41.86 


2511.60 


.5 




46.80 


2708.00 


.6 




51.26 


"3075.60 


.7 




55.36 


3321.60 


.8 




59.10 


3546.00 


.9 




62.60 


3756.00 


1. 




66.14 


3968.40 


1.1 




69.36 


4161.60. 


1.2 




72.44 


4346.40 


1.3 




75.39 


4523.40 


1.4 




78.21 


4692.60 


1.5 




80.96 


4857.60 


1.6 




83.59 


5015.40 


1.7 




86.16 


5169.60 


1.8 




88.65 


5319.00 


1.9 




91.27 


5476.20 


2. 




93.42 


5605.20 


2.1 




95.72 


5743.20 


2.2 




97.96 


5877.60 


2.3 




100.15 


6009.00 


2.4 




102.29 


6137.40 


2.5 




104.39 


6268.40 


2.6 




106.43 


6385.80 


2.7 




108.46 


6507.60 


2.8 




110.43 


6625.80 


2.9 




112.37 


6742.20 


3. 




114.28 


6856.80 


3.1 




116.15 


6969.00 


3.2 




118.00 


7080.00 


3.3 




119.81 


7188.60 


3.4 




121.60 


7296.00 


3.5 




123.36 


7401.60 



Application 1. — Air is exhausting from an orifice in an 
air duct into the atmosphere. The pressure of the air within 
the duct is one ounce by pressure gage or 1.74 inches of 



PLENUM WARM AIR HEATING 



253 



water by Pitot tube. Assuming' the air to be dry and the 
barometer 29.92 inches when the water in the tube and the 
air current are 60°, what is the theoretical velocity of the 
air? 

Solution. — By Tables XXX and XXXI, v = 86.97. Check 
this by Equation 76. 

Application 2. — In Application 1 let the duct pressure and 
temperature be 3 inches of water and 70° respectively. What 
is the theoretical orifice velocity? 

Solution. — From Table XXXI, v = 114.28 at 60°. Multi- 
plying this by 1.01 from Table XXXII = 115.42 F. P. S. 
velocity. Check by Equation 79. 

TABLE XXXIL 



m 

0) 


Factor for rel- 




Factor for rel- 




(P 


ative v e 1. at 


Factor for rel- 


ative vel. to 


Factor for rel- 


&fl 


same pressure 


ative pressure, 


move same wt. 


ative power to 




also relative 


also wt. of air 


of air also rel- 


move same wt. 


c 


powers to move 


moved at same 


ative pressure 


of air at vel. in 
column 4 and 




same vol. of air 


vel. = 


to produce the 


a 


at same vel. = 


460° + 60° 


vel. to move 


pressure in col- 


p 






same wt. of air 


umn 4 = factor 


S 
B 


/ Wt. at any 1 
\ Wt. .at 460° + 60° 


T 


i n column 4 


1 ^ Col. 3 


squared 


30 


.97 


1.07 


.93 


.87 


40 


.98 


1.04 


.96 


.92 


50 


.99 


1.02 


.98 


.96 


60 


1.00 


l.(X> 


l.W 


1.00 


70 


1.01 


.98 


1.02 


1.04 


SO 


1.02 


.96 


1.04 


.1.08 


90 


1.03 


.94 


1.06 


1.13 


UH) 


1.04 


.92 


1.00 


1.19 


125 


1.06 


.89 


1.12 


1.25 


1.50 


1.08 


.&5 


1.18 


1.39 


175 


1.10 


.82 


1.22 


1.49 


200 


1.13 


.79 


1.27 


1.61 


250 


1.17 


.73 


1.37 


1.88 


300 


1.21 


.68 


1.47 


2.16 


3.50 


1.25 


.64 


1..56 


2.43 


400 


1.28 


.60 


1.67 


2.79- 


500 


1..36 


..54 


1.85 


3.42 


600 


1.43 


.49 


2.04 


4.16 


700 


1.49 


.45 


2.22 


4.93 


800 


1..56 


.41 


2.44 


5.95 



145. Actual Amount of Air E]xhau.sted: — When air at 
any pressure is exhausted from one receptacle to another 
throug'h an orifice, nozzle or short pipe, the actual velocity 
is reduced below the theoretical velocity and the effective 



254 



HEATING AND VENTILATION 



area of the jet or stream is less than the actual area of the 
opening-. These variations are due to the shape of the inlet 
and the friction on the contact surface. To find the amount 
of air Q moved per second, multiply the theoretical velocity 
by the actual area and by a constant which is the product 
of the coefficient of reduced velocity and the coefficient of 
reduced area. Q = V r A, where C = constant, usually called 
coefficient of efflux. Kent, page 615, quotes from experiments 
by Weisbach the following- values: 
For conoidal mouthpiece, of form of the 

contracted vein, with pressures of 

from 0.23 to 1.1 atmospheres C = 0.97 to 0.99 

Circular orifice in thin plate C — 0.56 to 0.79 

Short cylindrical mouthpiece C — 0.81 to 0.84 

Short cyl. mouthpiece rounded at the inner 

end G — 0.92 to 0.93 

Conical converging- mouthpiece C — 0.90 to 0.99 

146. Results of Tests to Determine the Reltition be- 
tween Pressure and Velocity in Air Transmission: — In fan 
construction the number and shape of the blades, the sizes 
of the inlet and outlet openings, the shape and size of the 
casement around the wheel and the speed, all have an effect 
upon the relation between the pressure and the velocity of 
the air discharge. From tests conducted by the author, the 
curves shown in Fig-. 148 were obtained. A No. 2 Sirocco 




2 .3 4 .5 
RATIO or OPENING 
Fig. 148. 



PLENUM WARM AIR HEATING 255 

blower was belted to an electric motor and delivered air to 
a horizontal, circular pipe whose length was nine times the 
diameter. This pipe was provided with reducing- nozzles 
which varied the area of discharge by tenths from full open- 
ing to full closed. The air tube was provided also with 
manometer tubes for static, dynamic and velocity pressures, 
also, an adjustable scale reading in two positions, either .01 
or .002 inch of water. The gross power was taken by watt- 
meter and the delivered power from motor to fan was taken 
by dynamometer. In addition to this, the frictional horse- 
power of the fan and motor unit was obtained by removing 
the fan wheel from the shaft and taking readings with all 
other conditions remaining as nearly constant as possible. 
The frictional power, when deducted from the gross power 
recorded by the wattmeter, gave the readings for the net 
horse-power curve. A galvanized iron intake, enlarged from 
the size of the fan intake to a rectangular four square feet 
in area and divided by fine wires into squares to the size of 
the standard anemometer, was used to find the volume of air 
moved per minute. This volume is shown in the curve 
C. F. M. To check the curve, the volume was calculated for 
each opening by the Pitot tubes on the side of the experi- 
mental pipe. 

To fully understand this article, refer to Art. 29 and note 
that A, Fig. 12, registers static pressure plus velocity pressure. 
This sum may be called the dyniimic pressure. Also note that 
B registers only static pressure, i. e., that pressure which acts 
equally in all directions and serves no usefulness in moving 
the air. Also, note that A — 7? m C, i. e., dynamic pressure 
minus static pressure equals velocity pressure. When ap- 
plied in the form shown by (', the pressure recorded is that 
due to the velocity only. This is the form commonly used. 
Referring again to Fig. 148, A V P is that pressure recorded 
by V when applied to the air current at the fan outlet, = air 
velocity pressure. PVP is that pressure (obtained by Equa- 
tions 72 and 77) that would be shown on C if the air were 
moving as fast as the tip of the blades on the fan wheel, = 
peripheral velocity pressure. P V P = 1 in Fig. 148. D P 
is the dynamic pressure and would be found by applying A 
only. S P is the static pressure as stated above. 

In the tests, the fan was run a.t constant speed and the 
dynamic, static and velocity pressures were measured about 



256 



HEATING AND VENTILATION 



midway of the pipe at full opening-. Then the opening's were 
changed by 10 per cent, reductions until the pipe was fully 
closed and similar readings taken for each reduction. These 
readings "were plotted in the upper set of curves. Because 
the manometer tubes were located some distance from the 
end of the experimental pipe, there was a static pressure, 
ah, recorded at full opening. This caused the dynamic pres- 
sure to be raised a corresponding amount, a' h' . If the tubes 
had been located at the delivery end of the pipe the static 
and dynamic pressures would have fallen from & and 6' to 
a and a'. The peripheral velocity of the wheel was 2828 feet 
per minute and the corresponding pressure, with corrections 
for temperature, was found by Equation 75 to be .5 inch of 




2 .3 4 5 
RATIO QT OPENING 

Fig. 149. 



water. The relation between the peripheral velocity pres- 
sure and the air velocity pressure is shown in the upper 
curve, Pig. 149. In applying this to fan practice it shows 
the relation between the velocity of a point on the %vheel 
circumference and that of the air leaving the wheel. Notice 
that at full opening and discharging into free air, 
AVP : PVP :: 1.2 : 1. Since the velocities vary as the 
square roots of the pressures (r = \/2gh), we find the veloc- 
ities to be Vr20 : Vl"^ 1.1 : 1. That is to say, for this fan 
the air velocity at the free opening of the fan is 1.1 times 



PLENUM WARM AIR HEATING 257 

the peripheral velocity of the wheel. The corresponding- 
'x^elocity of air from a steel plate fan as reported by the 
American Blower Co. and as shown on the lower chart, is 
v. 45 : Vl = .67 : 1, or .61 of the speed of the Sirocco fan 
for the same wheel speed. The resistance offered by the 
ducts in the average plenum heating- system is equivalent, 
we will say, to that offered by a 75 per cent, gate opening in 
the experimental pipe. According to the diagrams for this 
opening, the ratio AVP to PVP is 1.04 for the Sirocco fan 
and .25 for the steel plate fan. The ratio of the air velocities 
to the peripheral velocities then are, respectively, VI. 04 : 
Vl~= 1.02 : 1 and V.~25~ : VT"^ .5 : 1. These show that with 
a 75 per cent, opening and with the fan wheels running with 
a peripheral velocity of 3000 feet per minute, the air would 
be entering the ducts at 1.02 X 3000 = 3060, and .5 X 3000 = 
1500 feet per minute respectively for the two types. Con- 
versely, if it were desired to have the air enter the ducts at 
1500 feet per minute, with a resistance equivalent to a 75 
per cent, opening, the fan wheels would have peripheral 
speeds of 1500 -^ 1.02 = 1470, and 1500 ^ .5 = 3000 feet per 
minute respectively. Prom these velocities may be obtained 
the wheel diameter for any given R. P. M. Other models of 
the Sirocco and multiple blade type of fans will show dif- 
ferent characteristics than the one under consideration. It 
will be seen from the above analysis that the change in con- 
struction from the steel plate type to the multiblade type 
permits a smaller wheel and fan to be installed for any given 
work desirable. From Equation 86 it is seen that the power 
required to drive a fan varies as the fifth power of the 
diameter and as the cube of the speed. With a given amount 
of air, Q, required per minute, the power will be diminished 
by reducing the diameter of the wheel or by reducing the 
speed of the fan. Manufacturers' catalogs should be con- 
sulted for capacities, sizes, etc. Such tables are supplied by 
the trade in form for easy reference and use. 

147. W^ork Performed and Horse-Po^ver Consumed in 
Moving- Air: — The foot pounds of work performed in moving 
air equals the product of the moving force into the distance 
moved through in any given time. Let pa — j)b = px = mov- 
ing force of air in ounces per square inch and A = cross- 
sectional area of air stream in square inches. Then the 



258 HEATING AND VENTILATION 

pounds per square inch will be px -=- 16, and the foot pounds 
of work, W, and tl: 
by the air will be 



of work, W, and the horse-power, H. P., absorbed per minute 



W = ^Z.l^pxAv (80) 

16 

2.75 pw A V 

H. P. = = .000114p«A7; (81) 

33000 

Equation 81 may be stated in terms of the cubic feet or air 
discharged per minute. Take the relation between px and hw 
at 60° as 12 px = 16 X .433 hw; also the relation Av = 144 Q 
when Q = cubic feet of air discharged per second and, from 
Equation 75, hw = v^ -i- 4356. Then by substituting in Equa- 
tion 81 

3.75 X .577 X 'i;^ X 144 Q 

H. P. = • =: .0000022 w2Q (g2) 

4356 X 33000 

In Equations 80 to 82, px = total pressure drop in system be- 
ing investigated (dynamic pressure), and v = velocity cor- 
responding to 2^,r. 

Illustration. — In a plenum heating and ventilating sys- 
tem the pressure above atmosphere at the fan outlet (gage 
pressure, corresponding to resistance of ducts and heater 
coils) is .6 inch of water; the pressure below atmosphere at 
the fan inlet (resistance of tempering coils and air inlet) is 
.15 inch of water; the equivalent velocity head is .25 inch of 
water; then the pressure the fan is working against is 1 inch 
of water = .58 ounce = px. 

Application 1.; — The constant area of a stream of dry air 
at 60° exhausting between the pressures of pa = 1% ounces 
and pb = V2 ounce, is 400 square inches. What is the work 
performed per minute and the horse-power consumed? (For 
velocity see second column Table XXX), 

W = 3.75 X (IV2 — V2) X 400 X 86.97 = 130500 foot 
pounds, and H. P. z= .000114 X (11/2 — V2). X 400 X 86.97 = 
3.96. 

Application 2. — A fan is delivering 1000000 cubic feet of 
air per hour to a heating system at a temperature of 100° 
and with a total pressure of % ounce. What is the theoret- 
ical horse-power of the fan? Prom Tables XXX and XXXII, 
V = 75.35 X 1.04 = 78.36 and 

//. P. = .0000022 X (78.36)2 ^ 278 = 3.76 



PLENUM WARM AIR HEATING 259 

The actual Jwrse- power of a blower fan is the horse-power 
' absorbed in moving- the air plus the horse-power absorbed 
by the blower. Let E = efficiency of the blower. Then Equa- 
tions 81 and 82 become 

.OOOlli pxAv 

H. P. = (83) 

E 
.0000022 i;2 g 

H. P. = (84) 

E 

The value of E changes with the type of fan. In the 
steel plate fan it will vary from. 20 to 40 per cent. Average 
L 30 per cent. In the Sirocco and multiblade fans it will vary 
from 50 per cent, at 50 per cent, rated capacity to 70 per cent, 
at 100 per cent, rated capacity. The latter value is safe 
(See also Art. 152). 

148. Carpenter's Practical Rules for Fan Capacities: — 

Professor Carpenter in H. & V. B. has summarized tests on 
steel plate fans as follows: 

Rule. — "The capacity of fans, expressed in cuTyic feet of air de- 
livered per minute, is equal to the cube of the diameter of the fan 
luheel in feet multiplied hy the number of revolutions multiplied by 
a coefficient having the following approximate value : for fan with 
single inlet delivering air without pressure, 0.6 ; delivering air with 
pressure of one inch, 0.5 ; delivering air unth pressure of one ounce, 
0.4 ; for fans with double inlets, the coefficient should be increased 
about 50 per cent. For practical purposes of ventilation, the ca- 
pacity of a fan in cubic feet per revolutio'ri will equal .4 the cube 
of the diameter in feet." 

Rule.-^"The delivered horse-power required for a given fan or 
blower is equal to the 5th pawer of the diameter in feet, multiplied 
by the cube of the number of revolutions per second, divided by one 
million and multiplied by one of the following coefficients : for free 
delivery, 30' ; for delivery against one cnmce pressure, 20 ; for de- 
livery against two ounces of pressure, 10." 

Stated as equations these rules are as follows: 



D =%j 



Cu. ft. of air per min. 



(85) 



C X RPM 
where D =r the diameter in feet and G = the coefficient, .4 



260 



HEATING AND VENTILATION 



for pressure of one ounce, .5 for pressure of one inch, and <* 
.6 for no pressure. 



H. P. 



Z>5 (Rp S)^ X C 
1000000 



(86) 



where G = SO for open flow, 20 for one ounce and 10 for two 
ounces pressure respectively. 

Note. — In using- Equations 85 and 86 for Sirocco or multi- 
vane fans, G should be 1.1, 1.2 and 1.3 for 85, and 100, 95 
and 90 for 86. 

149. Approximate Fan Sizes; — Table XXXIII gives sizes 
of important features in fan casing-, wheel and openings re- 
ferred to the wheel diameter. 



TABLE XXXIII. 



Diameter of wheel 

Diameter of inlet, single 

Dimensions of exhaust 

Wheel width inlet circum... 
Wheel width outer circum... 



Steel plate fan 




D 








.60 


D 


to 


.70 


,D 


.50 


D 


to 


.60 


D 


.50 


D 


to 


.60 


D 


.35 


D 


to 


.45 


D 



Multiblade fan 


D 






1.0 


D 


to 1.2 D 


.6 


D 


to .8 D 


by 


7 


D to 1.0 D 


.5 


D 





Type of fan 


Space 

occupied 

Full housed 


Discharge 
vert. 


Discharge 
horiz. 


Steel plate.. 


Length 


1.7 D to 1.5 D 

1.8 D to 2.0 D 


1.5 D to 1.7 D 


Multiblade 


1.4 D to 1.6 D 






Steel plate 


Height 


1.5 D to 1.7 D 
1.4 D to 1.6 D 


1 7 D to 1.5 D 


Multiblade 


1.8 D to 2.0 D 






Steel plate 


Width 


.7 D to 1.2 D 
1.3 D to 1.5 D 


.7 D to 1.2 D 


Multiblade 


1.3 D to 1.5 D 







PLENUM WARM AIR HEATING 



261 



150. Selection of Fan for Given Capacity; — By calculation. 
— (See Art. 153, Application 1). 

By (iraphical analysis. — Assume the conditions given in Art. 
153, Application 1, and apply Fig-. 150 as follows: locate 33330 
on the C F M scale, rise vertically from this point to the in- 



EXAMPLE SHOWING APPLICA- 
TION OP CURVES. 



Problem. Determine size of 
fan, revolutions per minute and 
brake horse-power required to de- 
liver 80,000 cubic feet per minute 
against a static pressure of 2.5" 
W. G. 

Solution. — Locate 80,000 on 
the C. F. M. scale and project ver- 
tically upward from this point to 
the intersection of that fan work- 




ing nearest 50% ratio opening at 
2.5" S. P., which in this case is 
Fan No. 13 (follow dash lines on 
curves). From this point project 
horizontally to intersect 2.5" S. P. 
curve and from thence upward 
parallel to horse-power lines to in- 
tersect Fan No. 13 at which point 
read 53.5 B. H. P. on horse-power 
scale to left. From same point on 
S. P. curve project vertically 
downward to intersect Fan No. 13 
reading 218 R. P. M. on scale to 
left. 



Fig. 150. 



tersection of that fan working nearest 50 per cent, ratio 
opening at 1 inch static pressure and find a No. 10 fan. Move 
horizontally to the left past the outlet velocity 1700 to the 
intersection with the 1 inch static pressure curve. Call this 



262 HEATING AND VENTILATION 

point A. From here drop vertically past the peripheral 
velocity 2850 feet per minute to the No. 10 slope and then *« 
move horizontally to the left to 180 revolutions per minute. 
Also, from A parallel the horse-power curve to the end, then 
rise to curve No. 10 and move horizontally to the left to 9 
horse-power. Check the peripheral and outlet velocities, 
also other values found, by Table 57, Appendix. 

Similar charts of loorkable size may lie had from the manufac- 
turers covering fans, Nos. 9 to 16 inchisive. 

151. Fan Drives: — Fans for heating and ventilating' pur- 
poses may be driven by simple horizontal or vertical, throt- 
tling or automatic steam engines, or by electric motors. In 
either engine or motor drives the power may be direct-con- 
nected or belt-connected to the fan. Direct-connected fan 
units make very neat arrangements but they require slow 
speed engines or motors and are frequently so large as to 
be prohibitive. Engine fans having poor attention are liable 
to pound, the noise carrying through the fan to the air cur- 
rent and up to the rooms. In belted drives engines or mo- 
tors are run at higher speeds and are either set off from the 
fan 10 feet or more to get good belt contact or used with a 
tightener. Chain drives are sometimes installed. They are 
positive in speed, fairly quiet in operation, permit the same 
speed reductions as belt drives and economize floor space. 

In deciding between engine or motor drives with steam 
coils, the steam from the engine should be considered a 
credit to the heating- system since it is exhausted into the 
heater coils and used instead of live steam from the boilers. 
Engines of high efficiency are not essential when the ex- 
haust steam can be used for heating. Enclosed engines run- 
ning in oil are preferred for high speeds. Belt drives should 
have the tight side below to increase the arc of contact. 

Electric motors should be specified for installations 
where exhaust steam can not be used, as in systems for 
ventilating only. They are more satisfactory in many ways 
than steam engines but are more expensive to operate. 
Direct current motors are desired in many places because 
of the convenience in obtaining speed changes and direct- 
connections. Alternating current motors operate at higher 
speeds, but may have speed reductions of 40 per cent, where 
required. When motors are specified the alternating current 
constant speed machine with belt drive is generally selected. 



TLENUM WARM AIR HEATING 



263 



153. Speed of the Fan: — A blower fan, exhausting into 
the open air, will deliver air with a lineal velocity approx- 
imately that of the peripheral velocity of the fan blades. If 
this same fan is connected to a system of ducts and heater 
coils, the lineal velocity of the air is reduced because of the 
increased resistance in the duct system. This causes the air 
to lag or slip between the fan blades and the casing-. In the 
average heating- system using multiblade fans this slip may 
be as great as 30 per cent. (See Art. 146). It is sometimes 
convenient in applying blowers to heating systems to con- 
sider the lineal velocity of the air as it leaves the fan to be 
two-thirds that of the periphery of the fan blades. Since 
the velocity of the air upon delivery from the fan should not 
exceed 1800 to 2500 feet per minute, the outer point on the 
fan blades should not be expected to move faster than 2700 
to 3750 feet per minute. Knowing this peripheral velocity, 
the revolutions per minute may be selected and the diameter 
obtained. 

In direct-connected fans the revolutions per minute must 
agree with those of the attached engine or motor. In belted 
fans this restriction does not apply. Ordinary blower fans 
running at high speeds are noisy and practice has deter- 
mined the number of revolutions to use. Table XXXIV gives 
speeds that may be recommended for such use. 

TABLE XXXIV. 
Speeds of Sirocco and Multiblade Blower Fans, in R P M 







Differential pressures 




Diameter 
of wheel 








.288 oz. 


.4.33 oz. 


..577 oz. 


.865 oz. 


1.1.54 oz. 


in inches 


.5 in. 


.7.5 in. 


lin. 


1.5 in. 


2 in. 


24 


322 


.S91 


454 


.554 


642 


m 


214 


200 


302 


369 


427 


48 


161 


196 


225 


277 


321 


CO 


129 


157 


181 


223 


257 


72 


107 


130 


151 


1&5 


214 


84 


92 


112 


1.30 


159 


184 


90 


86 


104 


121 


148 


171 


96 


81 


99 


113 


139 


160 



In recent developments in blower fans the number of 
blades has been increased and the depth of the blades has 
been diminished, making the operation of the fan somewhat 
similar to that of the steam turbine. These changes have 



264 HEATING AND VENTILATION 

produced higher efficiencies under test than were possible 
with the ordinary steel plate or paddle wheel fan. As a re- 
sult, fan sizes for given capacities have been reduced. 
Tables 55, 56 and 57, Appendix, give summaries of the latest 
catalog data. 

153. Selection of the Engine and Fan: — Determine the 

power of the fan from Equations 83 or 84. Assume a certain 

ratio between this and the engine power, say as 3 is to 4, 

then 

4 
H. P. of the engine = — //. P. of the fan (87) 

3 

Having obtained the horse-power of the engine, find the 

size of the cylinder as follows: let pa = absolute initial 

pressure of the steam in the cylinder, and 'r = number of 

the steam expansions in the cylinder = reciprocal of the per 

cent, of cut-off = the sum of the displacement at release 

plus the clearance divided by the sum of the displacement 

at cut-off plus the clearance. The cut-off allowed for high 

speed engines in power service approximates 25 per cent. 

stroke, but in engines for blower work this may be taken 

50 per cent, stroke. Find the mean effective .pressure, 2>i, by 

the equation 

1 + hyperbolic logarithm of r 
Pi = Pa back pressure (88) 

Let I = length of the stroke in inches and N = number of 
revolutions per minute and apply the equation 

2pilAN 

H. P. — (89) 

12 X 33000 

and find A, the area of the cylinder, from which obtain f7, 
the diameter of the cylinder. In applying Equation 89 it 
will be necessary to assume I. For engines operating blow- 
ers this may be taken 

2 Z ]V = 200 to 400 
Equation 88 assumes that the steam in the cylinder ex- 
pands according to the hyperbolic curve, p v = p' v' . For 
values of hyperbolic (Naperian) logarithms see Table 5, 
Appendix. It also assumes no loss in the recompression of 
the steam in the cylinder. Both assumptions are only ap- 
proximately correct, but the errors are slight and to a cer- 
tain degree, tend to neutralize each other, hence the final 



PLENUM WARM AIR HEATING 265 

results from this equation are near enoug-h to be used for 
fan engine calculations. For such work as this, r may be 
taken from 2 to 3. The back pressure should not be higher 
than 5 pounds g-ag-e (19.7 pounds absolute). This is deter- 
mined by the pressure in the coils carrying exhaust steam, 
which frequently drops to atmosphere or below. 

In determining the cylinder diameter and length of 
stroke it may be necessary to make two or more trial appli- 
cations before good sizes are obtained. When initial steam 
pressures are low, say not to exceed 30 pounds gage, mean 
effective pressures are small, thus requiring cylinders of 
large diaineter. In such cases the diameter of the cylinder 
may be greater than the length of stroke. "Where high 
pressure steam is used, say 100 pounds gage, the diameter 
of the cylinder will be less than the length of the stroke. 

Application 1. — Assume the following to fit the design 
shown in Figs. 151, 152 and 153; dry steam to the engine at 
100 pounds gage pressure; direct-connected unit; Sirocco 
type fan, single inlet, 60 per cent, efficiency, running at 180 
revolutions per minute and delivering 2000000 cubic feet of 
air per hour to the building against a static pressure of 1 
inch of water (total pressure 1.15 inch). (See Table 57, Ap- 
pendix); steam cut-off in the cylinder at one-third stroke 
and used in the coils at 5 pounds gage pressure. Find the 
sizes and horse-powers of the engine fan unit. 

From Equation 84, with v = velocity due to a total pres- 
sure of 1.15 inch of water, 

.0000022 X (71)- X 555.5 

Fan H. P. = = 10.26 

.60 

From extended tables of the A. B. Co. similar to Table 57, 

Appendix, find a No. 10 fan, 60 inch wheel, 33650 C. F. M., 181 

R. P. M., 10.2 H. P. Peripheral velocity of wheel 2845 F. P. M. 

Checking these values with Equations 85 and 86 



r, ^ ^ M 2000000 

D of fan = ^1 — 52 ft. = 62 in. 

^ 60 X 1.3 X 180 

(5.2)5 X (3)3 X 97 

10.1 









H. 


P. of fan 


— 


— " 





1000000 


F 


rom 


Equat 


ions 87, 


88 


and 


89. 








H. 


P. 


of 


engine 


- 


4 


X 


10.26 


= 13.68 



266 HEATING AND VENTILATION 

(1 + 1.0986 \ 
I — 19.9 = 60.5 lbs. per sq. in. 

It 2 I N = 250, Z = 250 ^ 360 = .69 ft. = 8.25 in. and 

13.68 X 12 X 33000 

A = = 30 sq. in. = 6.25 in. diameter. 

2 X 60.5 X 8.25 X 180 

The engine is 6.25 in. X 8.25 in., at 180 R. P. M. 

Application 2. — Assume the values as in Application 1, 
excepting- that the steam is taken from a conduit main at 
a pressure of 30 pounds per square inch gage, that 2 Z ^ = 
300, and that the steam cut ofC in the cylinder is at one-half 
stroke. As before, D of fan = 5.2 ft.; H. P. of fan = 10.26; 
and H. P. of engine — 13.68. The mean effective pressure is 

(1 + .6931 \ 
I — 19.9 = 18.2 lbs. per sq. in. 

13.68 X 12 X 33000 

A = = 83 sq. in., and the size of 

2 X 18.2 X 10 X 180 

the engine is 10.25 in. X 10 in., at 180 R. P. M. 

154. Piping: Connections Around Heater and Engine: — 

Where fans are run by steam power the steam supply pres- 
sure is higher than that in the coils and the liye steam must 
enter the coils through a pressure reducing valve. Where 
this reduction is made to 5 pounds or below, the live steam 
may enter the same main with exhaust steam from the en- 
gine, the back pressure valve on the exhaust steam line pro- 
viding an outlet to the atmosphere in case the pressure runs 
above the 5 pounds allowable back pressure. If the back 
pressure increases above 5 pounds, the efficiency of the en- 
gine is reduced. Where the condensation from the live 
steam is desired free from oil, a certain number of coils are 
tapped for exhaust steam and this condensation trapped to 
a waste or sewer, the other coils delivering to a receiver for 
boiler feed or other purposes as may be required. 

Every heating system should be fully equipped with 
pressure reducing valves, back pressure valves, traps, and a 
sufficient number of globe or gate valves on the steam sup- 
ply and gate valves on the returns to make the system 
flexible and responsive to varying demands. Supply and re- 
turn connections for heater stacks should be the same as for 
the amount of direct radiation that will condense the same 



PLENUM WARM AIR HEATING 



267 



amount of steam. Some eng-ineers advocate a water-seal of 
20 to 30 inches on the return end of each section, thus mak- 
ing each section independent in its action. Where the coils 
are very deep this is a benefit. 

155. Application to School Buildings; — Figs. 151, 152 and 
153, and Table XXXV show an application of plenum heat- 
ing and ventilating- to a school building. The table gives 
some of the calculated results. Most of the applications 
throughout Chapters X, XI and XII, also refer to this same 
building. 

The plans show the double duct system with plenum 
chamber and ducts laid just below the basement floor. The 
small arrows show the heat registers and vent registers for 
each room. The same stack which serves as a heat car- 
rier to the room on one floor serves as the vent stack for 
the corresponding room on the floor above, there being a 
horizontal cut-off between them. The cut-off at the heat 
register is curved to throw the current of heated air into the 
the room with the least possible friction or eddy currents, 

TABLE XXXV. 
Data Sheet for Figs. 151, 152, 153. 





Heat loss 




Heat loss 




Heat loss 




in B. t. u. 




in B. t. u. 




in B. t. u. 




per hour from 




per hour from 




per hour from 


Room 


room, not 


Room 


room, not 


Room 


room, not 




counting- 




counting- 




counting- 




ventilation 




ventilation 




ventilation 


1 


51,520 


11 


81,130 


21 


81,130 


2 


74,200 


12 


126,973 


22 


17,150 


3 


29,400 


13 


44,583 


23 


113,800 


4 


36,260 


14 


60,907 


24 


17,150 


5 


42,210 


15 


70,224 


25 


35,189 


6 


35,350 


16 


50,862 


26 


.53,438 


7 




17 


51,940 


27 


102,333 


8 


16,520 


18 


24,843 


28 


28,420 


9 


16,520 


19 


23,660 


29 


37,380 


10 


42,210 


20 


63,840 


30 


54,110 


Totals 


344,190 


Totals 


540,100 


Totals 


598,961 



268 



HEATING AND VENTILATION 




Fig. 151. 



PLENUM WARM AIR HEATING 



269 



<2 

5 






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Mi hH MT^ 



°^ -M >H Mjok ^ M H 



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1 



h=i i=i 1=1 i=M — ^ 



1 

\ / 


F I 
5 P 




F 


\ ' 


L . F 


L g [ 




0* ' 




c 


^.^ 


^ 








L 


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\ 


£■ 1 






/ \ 


(20) 




r 



Fig-. 152. 



270 



HEATING AND VENTILATION 



1 


1 1 1 1 1 1 


)- — 1 


.1=^ 


1==? 


1 — T t — 1 p:=a .t 


Is 

Si--" • 


! 


g 


c 

c 

-♦c 


\ / 

\ 


3 

: »- 


; 

I 
I 


ziii 






HEIATIICG AND Vt 

SECOND FUOOR 

CEILI 

WINE 


] 

1 i, 

I 

I 


c 
<-jc 


tf ^~^ 


^ 

s 


-yi 


\ 




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I 








i ^ 






in 










I 
„ I 


7 


1 


1 


— o a 


t 






\ 




D 
3 


1 
I 






c 
«-|c 




s 




y \ 


1 












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3 


(30) 






t=J t=^ t=J 


■^- 


t=i 


. 


I 

t=d tLd t=d 



Fig-. 153. 



PLENUM WARM AIR HEATING 271 

156. Application of Split System to School Building: — 

Fig's. 154, 155 and 156 show the plans of a school building 
heated by direct-radiation and ventilated by fan-coil system. 
These are included especially to show the arrangements of 
the ducts and indirect apparatus on the basement plan. 
Som.e of the principal points in the design of the indirect 
section of this plant are as follows: Air moved by the fan 
per minute, 30000 cu. ft. against a static pressure of % in. 
of water; fan, at a tip speed of 2700 f. p. m., requires 9 horse- 
power; motor horse-power, 12; 50" vento coils, 3 stacks deep, 
5" centers, arranged in two tiers of 16 sections each making 
a total of 96 sections; air warmed from — 10° to 80°; duct at 
A B, 15 sq. ft., velocity 1600 f. p. m.; at C I>, 9 sq. ft., velocity 
1500 f. p. m.; Sit E F, 1 sq. ft., velocity 1550 f. p. m., and at 
(r M, 2.5 sq. ft., velocity 1150 f. p. m. ; fresh air inlet grill 48 
sq. ft., covered by y^" niesh wire screen; individual exhaust 
ventilation for toilets and showers; automatic regulation on 
all direct radiation in all class rooms and on two of the three 
complete stacks in the vento heaters. To supply the coils 
and the direct radiation required three cast iron sectional 
boilers, each having a rated capacity of 8350 sq. ft. of direct 
steam radiation. 



272 



HEATING AND VENTILATION 




riiiiiiiiiiii 




[mnmrtn 



^H 



© 



® 







mum 



Fig. 154. 



PLENUM WARM AIR HEATING 



273 




Fig. 155. 



!74 



HEATING AND VENTILATION 




Fig. 156. 



CHAPTER XIII. 



DISTRICT HEATING OR CENTRALIiJED HOT WATER 
AND STEAM HEATING. 



GENERAL. 

157. Heating Residences and Business Blocks from a 
central station is a method that is being- employed in many 
cities and towns throughout the country. The centralization 
of the heat supply for any district in one large unit has an 
advantage over a number of smaller units in being able to 
burn the fuel more economically, and in being able to re- 
duce labor costs. It has also the advantage, when in con- 
nection w^ith any power plant, of saving the heat which 
would otherwise go to waste in the exhaust steam and stack 
gases, by turning it into the heating system. The many 
electric lighting and pumping stations around the country 
give large opportunity in this regard. Since the average 
steam power plant is very wasteful in these two particulars, 
any saving that might be brought about should certainly be 
sought for. On the other hand, however, a plant of this 
kind is at a disadvantage in that it necessitates transmit- 
ting the heating medium through a system of conduits, which 
generally is a wasteful process. The failure of many of the 
pioneer plants has cast suspicion upon all such enterprises 
as paying investments, but the successful operation of many 
others shows the possibilities, where care is exercised in 
their design and operation. 

158. Important Considerations in Central Station Heat- 
ing: — In any central heating sj^stem, the following consider- 
rations w^ill go far toward the success or the failure of the 
enterprise: 

First. — There should be a demand for the heat. 

Second. — The plant should be near to the territory heated. 

Third. — There should be good coal and water facilities at 
the plant. 

Fourth. — The quality of all the materials and the instal- 
lation of the same, especially in the conduit concerning in- 



276 HEATING AND VENTILATION 

sulation, expansion and contraction, and durability, are 
points of unusual importance. 

Fifth. — The plant must be operated upon an economical 
basis, the same as is true of other plants. 

Sixth. — The load-factor of the plant should be hig^h. This 
is one of the most important points to be considered in com- 
bined heating- and power work. The g-reater the proportion 
of hours each piece of apparatus is in operation, to the total 
number of hours that the plant is run, the g-reater the plant 
efficiency. The ideal load-factor requires that all of the ap- 
paratus be run at full load all the time. 

The average conduit radiates a g'reat deal of heat, hence, 
the nearer the plant to the heated district the greater the 
economy of the system. Likewise a location near a railroad 
minimizes fuel costs, and g^ood water, with the possibility 
of saving- the water of condensation from the steam, assists 
in increasing- the economy of the plant. It is to be expected 
that even a well desig-ned plant, unless safeg-uarded ag-ainst 
ills as above sug-gested, would soon succumb to inevitable 
failure. 

Two types of centralized heating- plants are in use, hot 
toater and steam. Each will be discussed separately. In the. 
discussion of either system, certain definite conditions "will 
have to be met. First of all, there should be a demand in 
that certain locality for such a heating- system, before the 
plant can be considered a safe investment. To create a de- 
mand requires g-ood representatives and a first-class resi- 
dence or business district. When this demand is obtained 
the plan of the probable district to be heated will first be 
platted and then the heating- plant will be located. In many 
cases the heating- plant v/ill be an added feature to an al- 
ready established lig-hting- or power plant and its location 
will be more or less a predetermined thing-. 

In addition to these material and financial features just 
mentioned, one must consider the legal phases that always 
come up at svich a time. These relate chiefly to the franchise 
requirements that must be met before occupying- the streets 
■with conduit lines, etc. All of these considerations are a 
part of the one g-eneral scheme. 

159. The Scope of the Work in central station heating 
may be had from the following- outline: 



DISTRICT HEATING 



277 



( Hot Water Heating- 
by use of 



Central Sta- 
tion Heating-< 



Steam Heating. 



Exhaust steam heaters 
Live steam heaters 
Heating boilers 
Economizers 
Injectors or 
I Com-minglers 

( Exhaust steam 
1 Live steam 



In the liot water system the return water at a lowered tem- 
perature enters the power plant, is passed through one or 
more pieces of apparatus carrying live or exhaust steam, or 
flue gases, and is raised in temperature again to that in the 
outgoing main. From the above, a number of combinations 
of reheating can be had. Any or all of the units may be put 
in one plant and the piping system so installed, that the 
water will pass through any single unit and out into the 
main; or, the water may be split and passed through 
units in series. All of these combinations are possible, but 
not practicable. In most plants, two or three combinations 
only are provided. In the existing plants the order of pref- 
erence seems to be, exhaust steam reheaters, economizers, 
heating boilers, injectors or com-minglers, and live steam 
heaters. 

All of the above pieces of reheating apparatus operate 
by the transmission of heat through metal surfaces, such as 
brass, steel or cast iron tubes, excepting the com-mingler, 
this being simply a barometric condenser* in which the ex- 
haust steam is condensed by the injection water from the re- 
turn main, the mixture being drawn directly into the pumps. 

The objection to the tube transmission is the lime, mud 
and oil deposit on the tube surfaces, thus reducing the rate 
of transmission and requiring frequent cleaning. The ob- 
jections to the com-minglers are, first, that the pump must 
dra'vv'- hot water from the condenser and second, that a cer- 
tain amount of the oil passes into the heating line. With 
perfected apparatus for removing the oil, the com-mingler 
will no doubt supersede, to a large degree, the tube re- 
heaters in hot water heating-. 



278 HEATING AND VENTILATION 

In the steam system the proposition is very much simpli- 
fied. The exhaust steam passes through one or more oil 
separating- devices and is then piped directly to the header 
leading to the outgoing main. Occasionally a connection is 
made from this line to a condenser, such that the steam, 
when not used in the heating system, may be run directly 
to the condenser. These pipe lines, of course, are all prop- 
erly valved so that the current of steam may easily be de- 
flected one way or the other. In addition to this exhaust 
steam supply, live steam is provided from the boiler and 
enters the header through a pressure reducing- valve. In 
any case when the exhaust steam is insufficient the supply 
may be kept constant by automatic regulation on the reduc- 
ing- valve. 

In selecting between hot water and steam systems the 
preference of the engineer is very largely the controlling- 
factor, The preference of the engineer, however, should be 
formed from facts and conditions surrounding- the plant, and 
should not come from mere prejudice. The following- points 
are some of the important ones to be considered: 

First cost of plant installed. — This is very much in favor of 
the steam system in all features of the power plant equip- 
ment, the relative costs of the conduit and the outside work 
being very much the same in the two systems. 

Cost of operation. — This is in favor of the hot water sys- 
tem because of the fact that the steam from the engines 
may be condensed at or beloAV atmospheric pressure, -while 
the exhausts from the engines in the steam systems must 
be carried from five to fifteen pounds gage, which naturally 
throws a heavy l^ack pressure upon the engine piston. 

Pressure in circulating mains. — This is in favor of the steam 
system. The pressure in any steam radiator will be only 
a few pounds above atmosphere, while in a hot water sys- 
tem, connected to high buildings, the pressure on the first 
floor radiators near the level of the mains becomes very 
excessive. The elevation of the hig-hest radiator in the 
circuit, therefore, is one of the determining factors. 

Regulation. — It is easier to regulate the hot water system 
without the use of the automatic thermostatic control, since 
the temperature of the water is maintained according- to a 
local schedule which fits, all degrees of outside temperature. 



DISTRICT HEATING 279 

When automatic control is applied, this advantage is not so 
marked. 

Returning the water to the poioer plant. — In most steam plants 
the water of condensation is passed through indirect heaters 
to remove as much of the remaining- heat as possible and 
is then run to the sewer. This procedure incurs a consider- 
able loss, especially in cold weather when the feed water 
at the power plant is heated from low temperatures. This 
point is in favor of the hot water system. 

Estimating charges for heat. — This is in favor of the steam 
system since, by meter measurement, a company is able to 
apportion the charges intelligently. The flat rate charged 
for water heating and for some steam heating is in many 
cases a decided loss to the company. 

160. Conduits: — In installing conduits for either hot 
water or steam systems the selection should be made after 
determining, first, its efficiency as a heat insulator; second, 
its initial cost; third, its durability. Other points that must 
be accounted for as being very essential are: the supporting, 
anchoring, grading and draffiing of the mains; provision for 
expansion and contraction of the mains; arrangements for 
taking ofE service lines at poinds where there is little move- 
ment of the mains; and the draining of the conduit. 

Some conduits may be installed at very little cost and 
yet may be very expensive propositions, because of their in- 
ability to protect from heat losses; while, on the other hand, 
some of the most expensive installations save their first 
cost in a couple of years' service. Many different kinds of 
insulating materials are used in conduit work such as mag- 
nesia, asbestos, hair felt, wool felt, mineral wool and air cell. 
Each of these materials has certain advantages and under 
certain conditions would be preferred. It is not the real 
purpose here to discuss the merits of the various insulators, 
because the quality of the workmanship in the conduit en- 
ters into the final result so largely. The different ways that 
pipes may be supported and insulated in outside service will 
be given, with general suggestions only. Figs. 157 and 158 
show a few of the many methods in common use. A very 
simple conduit is shown at A. This is built up of wood sec- 
tions fitted end to end, covered with tarred paper to prevent 
surface water leaking in and bound with straps. The pipe 
either is a loose fit to the bore and rests upon the inner sur- 



280 HEATING AND VENTILATION 

face, or is supported on metal stools, driven into the wood or 
merely resting upon it. Stools hold the pipe concentric with 
the inner bore of the log'. With much end movement of the 
pipe, from expansion and contraction, stools should not be 
used unless they are loose and have a wide surface contact 
with the wood. A metal lining- with the pipe resting di- 
rectly upon it is considered good. The conduit is laid to a 
good str'aight run in a gravel bed and usually over a small 
tile drain to carry off the surface water, excepting as this 
drain is not necessary in sections where there is good gravel 
drainage. The insulation in A is only fair. The air space 
around the pipe, however, is to be commended. li is an 
improvement over A and is built up of boards notched at 
the edges to fit together. The materials used, from the 
outside to the center, are noted on the sketch beginning 
with the top and reading down. This covering is in general 
use and gives good satisfaction from every standpoint. C 
shows a good insulation and supports the pii)e upon rollers 
at the center of a line of halved, vitrified tile. The lower 
half of the tile should be graded and the pipe then run 
upon the rollers, after which it may be covered with some 
prepared covering and the remaining space next the tile 
filled with asbestos, mineral wool or other like material. D 
shows the same adapted to basement work. Occasionally two 
pipes are run side by side, main and return, in which case 
large halved tiles may be used as in W, having large metal 
supports curved on the lower face to fit the tile. If these 
supports are not desired the same kind of straight tiles 
may be used with a tee tile inserted every 8 to 12 feet 
having the bell looking down as in F. In this bell is built 
a concrete setting with iron supports for the pipes which run 
on rollers. These rollers are sometimes pieces of pipes cut 
and reamed, but are better if they are cast with a curvature 
to fit the pipes to be supported. This form of conduit, when 
drained to good gravel, gives first-class service. (1, If and / 
show box conduits with two or more thicknesses of % inch 
boards nailed together for the sides, top and bottom. The 
bottom of the conduit is first laid and the pipe is run. The 
sides are then set in place and the insulating material put 
in, after which the top is set and the whole filled in. I shows 
the best form of box, since with the air spaces this is a 
very good insulator. All wood boxes are very temporary,' 



DISTRICT HEATING 



281 



'^^^y ''_■>■(■- ^^^- ' ^^ ■'' ^-f ^^y'-' --^ 




Fig-. 157. 



282 



HEATING AND VENTILATION 




STONE 

, BRIOK- 

^MIN WOOL 

hA/OOD 

HNSULATION 

^— PIPE 

#t^ROLL^P? 
^■'^ -RAVEL 
DRAIN 

H L 





y x/> /xyy / • J )/ //y// '//// 



GRAVEL 
-WOOD 
-INSULATION 
-PIPE 
-ROLLER 




STONE 
SLATE 
CEMENT 
HALVED TILE^ 
COVERING^ 
PIPE 
PIPE SUPP 



STONE 
CEMENT 

PIPE 
SUPPORT 



Fig-. 158. 




M 



DISTRICT HEATING 283 

hence, brick and concrete are usually preferred. K is a 
conduit with 8 inch brick walls covered with flat stones or 
halved g-lazed tiles cemented to place to protect from sur- 
face leakage. The bottom of the conduit has supports built 
in every 8 to 12 feet, and between these points the conduit 
drains to the graA^el. The usual rod and roller here serve 
as pipe supports. The pipe is covered with sectional cover- 
ing- and the rest of the space may or may not be filled with 
vsrool or chips, as desired. L shows the sectional covering 
omitted and the entire conduit filled with mineral wool, hair 
felt or asbestos. M has the supporting rod built into the 
sides of the conduit and has the bottom of the conduit 
bricked across and cemented to carry the leaks and drainage 
to some distant point. ]<[ shows a concrete bottom with 
brick sides, having the pipe supporte.d upon cast iron stand- 
ards. The latest conduit has concrete slabs for bottom and 
sides and has a reinforced concrete slab top. This comes as 
near being permanent as any, is reasonable in price, and 
when the interior is filled with good non-conducting ma- 
terial, or when the pipe is covered with a good sectional 
covering, it gives fairly high efficiency. 

All conduit pipes should be run as nearly uniform in 
grade as possible to avoid the formation of air and water 
pockets. Any unusual elevation in any part of the main 
may require an air vent being placed at the uppermost point 
of the curve, otherwise air may collect in such quantities as 
to retard circulation. All low points in the steam lines m^ust 
be drained to traps. 

The lieat loss from conduits is an item of considerable im- 
portance. A good quality of materials and insulation will 
probably reduce this loss as low as 20 to 25 per cent, of the 
amount lost from the bare pipe. To show the method of 
analysis and to obtain an estimate of the average conduit 
losses, the following application will be made to a supposed 
two-pipe hot water system. The loss of heat in B. t. u. per 
lineal foot from any pipe per hour may be taken from the 
equation 

He - KCA {t — /') (90) 

where K = rate of transmission for uncovered pipes, C = 100 
per cent. — efficiency of the insulation, A = area of pipe sur- 
face per lineal foot of pipe, t = average temperature on the 



284 



HEATING AND VENTILATION 



inside of the pipe and t' 
side of the conduit. 



average tempei^ature on tlie out- 



Application. — Having- given a system of conduit pipes 
(two pipes in one conduit) with sizes and lengths as stated 
in the first and second columns of Table XXXVI, what is the 
probable heat loss in B. t. u. per hour on a winter day and 
what is the radiation equivalent in a hot water system car- 
rying water at an average temperature of 170 degrees? 

TABLE XXXVI. 





Total lineal 


Surface per 


B. t. u. per hr. 


Equivalent 


Pipe size 


feet of main 


foot of length 


per lineal foot 


no. of sq. ft. 


inches 


and return 


A 


He 


of H. W. Rad. 


2 


50OO 


.62 


48.8 


1435 


3 


2000 


.&1 


71.6 


842 


4 


3000 


1.06 


83.4 


1472 


6 


3000 


1.73 


137.1 


2420 


8 


200O 


2.26 


177.9 


2093 


10 


2000 


2.83 


221.9 


2611 


12 


2O0O 


3.33 


262.0 


3082 


14 


lOOO 


4.00 


314.8 


1852 


Totals. B. t 


. u. lost per ho 


ur 2687100 




15807 



If K = 2.25, C = 100 — 75 = 25 per cent., t = 175 and 
r = 35, we have for a 2-inch pipe, He = 2.25 X .25 X .62 X 
140 = 48.8, which for 5000 lineal feet = 244000 B. t. u., and 
for the entire system, 2687100 B. t. u. If each square foot of 
hot water radiation gives off 170 B. t. u. per hour then the 
radiation equivalent for the 2-inch pipe is 244000 -^ 170 = 
1435 square feet. Similarly w^ork out for each pipe size and 
obtain the values given in the last column of the table. This 
conduit loss is sufficient to heat 15807 square feet of radia- 
tion in the district. In terms of the coal pile it approxi- 
mates 350 pounds per hour. Now assuming the 14 inch main 
to supply the entire district at a velocity of 6 feet per second 
we have approximately 162000 square feet of H. W. surface 
on the line. From this the line loss is 15807 -^ 162000 = 9.1 
per cent. It should be remembered that the above assumes 
the plant working under a heavy load, when the per cent. 



DISTRICT HEATING 285 

of line loss is a minimum. This loss remains fairly constant 
while the heat utilized in the district fluctuates greatly. In 
mild weather, therefore, the per cent, of line loss to the total 
heat transmitted is much greater. 

161. Layout of Street Mains and Conduits? — No definite 
information can be given concerning the layout of street 
mains, because the requirements of each district would call 
for independent consideration. The following general sug- 
gestions, however, can be noted as applying to any hot 
water or steam system: 

Streets to be used. — Avoid the principal streets in the city, 
especially those that are paved; alleys are preferred because 
of the minimum cost of installation and repairs. 

Cutting of the mains. — Do not cut the main trunk line for 
branches more often than is necessary. Provide occasional 
by-pass lines between the main branches at the most im- 
portant points in the system, so that, if repairs are being 
made on any one line, the circulation beyond that point may 
be handled through the by-pass. Such by-pass lines should 
be valved and used only in case of emergency. 

Offsets and expansion joints. — Offsets in the lines hinder the 
free movement of the water and add friction head to the 
pumps; hence, in water systems, the number should be re- 
duced to a minimum. Long radius bends at the corners re- 
duce this friction. Offsets are especially valuable to take 
up the expansion and contraction of the piping without the 
aid of expansion joints. This is illustrated in Fig. 159, where 
anchors are placed at A, and the gradual bending of the 
pipes at each corner makes the necessary allowance. The 
expansion in wrought iron is about .00008 inch per foot per 
degree rise in temperature; hence in a hot water main the 
lineal expansion between 0° and 212° is .017 inch per foot of 
length or 1.7 inches for each 100 feet of straight pipe. In 
hot water heating systems the temperature of this pipe 
would never be less than 50°, which would cause an expan- 
sion from hot to cold of only .013 inch per foot, or 1.3 inches 
for each 100 feet of straight pipe. In steam systems the 
pipe temperature may vary anywhere from 50° to 300°, 
making a lineal expansion of .02 inch per foot of length or 2 
inches for each 100 feet of straight pipe. As here shown the 







D -^^ 


ffl-ffl^ 


A 


♦M 



Fig-. 159. 



286 HEATING AND VENTILATION 

movement from the anchor 
at A toward B may be ab- 
sorbed by the swinging of the 
pipe about 0. B.B. should 
therefore be as long- as possi- 
ble to .avoid unduly straining- 
the pipe at the joints. Allow- 
ing a maximum movement of 
6 inches for each expansion 
joint, the anchors would be spaced 500 and 300 feet center 
to center respectively, for hot water and steam mains. These 
figures would seldom be exceeded, and in some cases would 
be reduced, the spacing depending- upon the type of expan- 
sion joint used. Ordinarily, 400 feet spacing can be recom- 
mended for hot water and 300 feet for steam. If the city 
layout meets this value fairly well, then the expansion joints 
and anchors may be made to alternate with each other, one 
each to every city block. 

A few of the expansion joints in common use are shown 
in Pig, 160. A is the old slip and packed joint. This joint 
causes very little trouble except that it needs repacking 
frequently. It is very effective when properly cared for. 
The slip joint should have bronze bearings on both the 
outside of the plug and the lining of the sleeve. The ends 
of the plug- and sleeve may be screwed for small pipes, or 
flanged for larg-e ones. B show^s an improved type of slip 
joint, having a roller bearing- upon a plate in the bottom 
of the conduit, and plugs bearing- ag-ainst metal pla.tes along 
the sides of the conduit to keep it in line. C and D show 
other slip joints very similar to A and B. C has one ball 
and socket end to adjust the joint to slight changes in the 
run of the pipe, and D has two packings enclosing the plug 
to give it rigidity. The drainage in each case is taken off 
at the bottom of the casting. E has two larg-e flexible disks 
fastened to the ends of the pipe and separated from each 
other by an annular ring casting-. These disks are frequently 
corrugated, are usually of copper and are very large in 
diameter so that the pipe has considerable movement with- 
out endangering- the metal in the disks. F has a corrugated 
copper tube fastened at the ends to the pipe flanges. This 
is protected from excessive internal pressure by a straight 
tube having a sliding flt to the inside of the flanges, thus 
allowing for end movement. O is very similar to E. It has, 



DISTRICT HEATING 



287 








L^~-^l^ 



3> 







Fig-. 160. 



288 



HEATING AND VENTILATION 



however, only one copper disk. This disk is enclosed in a 
cast iron casement, one side of which is open to the at- 
mosphere, the other side having- the same pressure as within 
the pipe. H is very similar to E, having two copper dia- 
phrag-ms to take up the movement. These diaphragms flex 
over rings with curved edges and are thus protected some- 
what against failure. / shows a copper U tube which is 
sometimes used. This is set in a horizontal position and the 
expansion and contraction is absorbed by bending the loop. 
In all these joints those which depend upon the bending of 
the metal require little attention except where complete 
rupture occurs. In old plants, however, the rupturing of 
these diaphragms is of frequent occurrence. The packed 
joint requires attention for packing several times in the 
year, but very seldom causes trouble other than this. 

Anchors. — In any long run of pipe, where the expansion 
and contraction of the pipe causes it to shift its position 
very much, it is necessary to anchor the pipe at intervals so 
as to compel the movement toward certain desired points. 
The anchor is sometimes combined with the expansion joint, 
in which case the conduit work is simplified (See Fig. 161). 

Service pipes to residences are preferably taken off at 




DISTRICT HEATING 



289 



or near the anchors. All condensation drains in steam mains 
are likewise taken off at such points. 

Valves. — All valves on water systems should be straight- 
way gate valves. Valves on steam systems should be gate 
valves on lines carrying condensation, and may be renewable 
seat globe valves on the steam lines. Valves should be 
placed on the main trunk at the power plant, on all the prin- 
cipal branch mains as they leave the main trunk, on all 
by-pass lines, on all the service mains to the houses, and at 
such important points along the mains as will enable certain 
portions of the heating district to be shut off for repairs 
without cutting out the entire district. 

Manholes. — Manholes are placed at important points along 
the line to enclose expansion joints and valves. These man- 
holes are built of brick or concrete and covered with iron 
plates, flag stones, slate or reinforced concrete slabs. Care 
must be exercised to drain these points well and to have the 
covering strong enough to sustain the superimposed loads. 

162. Typical Design for' Consideration: — In discussing 
district heating, each important part of the design work will 
be made as general as possible and will be closed by an 



DDD 






no 



BUSINESS 















1 

1 1 






1 

1 




















1 

RE 

1 


1 1 1 
SIDENCC 
1 II 




1 







RESIDENCE. 



nnnn 




290 



HEATING AND VENTILATION 



application to the following concrete example which refers 
to a certain portion of an imaginary city (Pig. 162) as avail- 
able territory. A city water supply and lighting plant is 
located as shown, with lighting and power units aggregat- 
ing 475 K. W., city water supply pumps aggregating 3000000 
gallons maximum capacity, and smaller pumps requiring ap- 
proximately 15 per cent, of the amount of steam used by 
the larger lighting units. It is desired to re-design this 
plant and to add a district heating system to it; the same to 
have all the latest methods of operation and to be of such a 
size as to be economically handled. Fig. 169 shows the es- 
sential details of the finished plant. 

163. Electrical. Output and Exliau.st Steam Available for 
Heating: Purposes from the Power Units; — In the operation 
of such a plant, one of the principal assets is the amount of 
exhaust steam available for heating purposes. The amount 
may be found for any time of the day or night by construct- 
ing a power chart as in Fig. 163, and a steam consumption 
chart as in Fig. 164. Referring to Fig. 163, the values here 



500 



400 



300,, 



2009 



100 



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2 3 4 5 
AM 



9 10 II 12 I 2 3 4 5 6 7 6 9 10 II 12 

M PM 

HOURS 
Fig. 163. 



given are assumed, for illustration, to be those recorded at 
the switchboard of the typical plant on a day when heavy 
service is required. The curves show that the 75 K. W. unit 
runs from 12 P. M. to 7 A. M. and from 6 P. M. to 12 P. M. 
with an output of 25 A'. W. It also runs from 7 A. M. to 10 A. 
M. and from 4 P. M. to 6 P. M. under full load. The 150 K. W. 



DISTRICT HEATING 



J91 



unit runs from 4 A. M. to 7 A. M. with an output of 100 K. W. 
and then increases to 125 K. W. for the entire time until 6 P. M. 
when it is shut down. The 250 K. W. unit is started up at 7 
A. M. and runs until 6 P. M. under full load, when the load 
drops off to 150 A'. W. and continues until 10 P. M. when the 
unit is shut down, leaving- only the 75 K. W. unit running-. 
The heavy solid line shows all the power curves superim- 
posed one upon the other. Having given the K. W. output, 
the general equation for determining the horse-power of the 
engines is 

K. W. X 1000 

I. H. P. = (91) 

746 X -E X E' 

where E and E' are the efficiencies of the generator and en- 
g-ine respectively. If we assume the efficiency of the gener- 
ator to be 90 per cent., and that of the engine to be 92 per 
cent., then Equation 91 becomes 
K. TF. X 1000 



I. H. P. 



:rr approx. 1.62 K. W. 



(92) 



746 X .90 X .92 
Assuming that the 250 K. W. unit consumes 24 pounds, the 
150 K. W. unit 32 pounds, and the 75 K. W. unit 32 pounds of 
steam per I. H. P. hour respectively, when running under 











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12 i 2 3 4 5 
AM 



9 10 II 12 I 2 3 4 5 6 7 8 9 10 II 12 

M ' PM 

HOURS 

Fig. 164. 



292 HEATING AND VENTILATION 

normal loads, the total steam consumed in the three units 
at any time is shown by the lower curve in Fig. 164. The 
upper curve shows the 15 per cent, added allowance for 
smaller units not included in the above list. The values 
assumed for efficiencies and the values for steam consump- 
tion are reasonable and may be used if a more exact figure 
is not to be had. 

It will be seen that the maximum steam consumption in 
the generating- units in the power plant is 23100 pounds per 
hour and the minimum is 1490 pounds per hour. These two 
amounts, together with the exhaust steam from the circu- 
lating- pumps on the heating- system, if a hot water system 
is installed, and that from the pumps in the city water 
supply, will determine the capacity of the exhaust steam 
heaters on the hot water supply and the capacity of the 
boilers or economizers to be used as heaters when the 
exhaust ^team is deficient. 

164. Amount of Heat Available for Heating Purposes 
in Kxliaust Steam, Comfiared ^vitli Tliat in Saturated Steam 
at the Pressure of the E^xhaust: — To study the effect of ex- 
haust steam upon heating problems and to determine, if 
possible, the theoretical amount of heat given off with the 
exhaust steam under various conditions of use, make several 
applications: first, to a simple high speed non-condensing 
engine using saturated steam; second, to a compound Corliss 
non-condensing engine using saturated steam; third, to the 
first application when superheated steam is used instead of 
saturated steam; and fourth, to a horizontal reciprocating 
steam pump. Assume the following safe conditions. Case 
one — boiler pressure 100 pounds gage; pressure of steam 
entering cylinder 97 pounds gage; quality of steam at 
cylinder 98 per cent.; steam consumption 34 pounds per 
indicated horse-power hour; one per cent, loss in radiation 
from cylinder; and exhaust pressure 2 pounds gage. Case 
two — boiler pressure 125 pounds gage; pressure at high 
pressure cylinder 122 pounds gage; quality of steam enter- 
ing high pressure cylinder 98 per cent.; steam consumption 
22 pounds per indicated horse-power hour; 2 per cent, loss 
in radiation from cylinders and receiver pipe, and exhaust 
pressure 2 pounds gage. Case three — same as case one with 
superheated steam at 150 degrees of superheat. Case four — 
as stated later. 



DISTRICT HEATING 293 

The number of B. t. u. exhausted with the steam, in 
any case, is the total heat in the steam at admission, minus 
the heat radiated from the cylinder, minus the heat ab- 
sorbed in actual work in the cylinder. 

High Sfieed engine. Case one. — Let r = heat of vaporiza- 
tion per pound of steam at the stated pressure, x = quality 
of the steam at cut-off, q = heat of the liquid in the steam 
per pound of steam, and Ws = pounds of steam per indicated 
horse-power hour. From this the total number of B. t. u. 
entering- the cylinder per horse-power hour is 

Total B. t. u. = Ws {xr -\- q) (93) 

From Table 4, r = 881, x = .98 and q = 307; then if W. = 34, 
initial B. t. u. = 34 (.98 X 881 + 307) = 39792.92. Deducting 
the heat radiated from the cylinder we have 39792.92 x .99 = 
39395 B. t. u. per horse-power left to do work. The B. t. u. 
absorbed in mechanical work (useful work + friction) in 
the cylinder per horse-power hour is (33000 X 60) 4- 778 = 
2545 B. t. u. Subtracting- this work loss we have 39395 — 
2545 = 36850 B. t. u. given up to the exhaust per horse-power 
hour. Comparing this value with the total heat in the same 
weight of saturated steam at 2 pounds gage, we have 
100 X 36850 ^ (34 X 1152.8) = 94 per cent. 

Compound Corliss engine. Case two. — With the same terms 
as above let r = 869, x = .98, q = 322.8, and Ws = 22, then 
the initial B. t. u. = 22 (.98 X 869 -f- 322.8) = 25837. Less 
2 per cent, radiation loss = 25837 X .98 = 25321 B. t. u. 
The loss absorbed in doing mechanical work in the cylinder 
per horse-power is, as before, 2545 B. t. u. Subtracting this 
we have 25321 — 2545 = 22776 B. t. u. given up to the ex- 
haust per horse-power hour. Comparing as before with 
saturated steam at 2 pounds gage, we have 100 X 22776 -f- 
(22 X 1152.8) = 90 per cent. 

Case three. — Now suppose superheated steam be used in 
the first application, all other conditions being- the same, 
the steam having 150 degrees of superheat, what difference 
will this make in the result? The total heat entering the 
cylinder now is the total heat of the saturated steam at 
the initial pressure plus the heat given to it in the super- 
heater. Let Cp = specific heat of superheated steam and 



294 HEATING AND VENTILATION 

td = the degrees of superheat, then the total heat of the 
superheated steam is 

Total B. t. u. (sup.) = Ws (xr + q + Cpta) (94) 

This for one horse-power of steam (34 pounds), if the 
specific heat of superheated steam is .54, will be 34 X -99 X 
(1188 + .54 X 150) = 42714.5 B. t. u. and the heat turned 
into the exhaust will be 42714.5 — 2545 = 40169.5 B. t. u. 
Comparing- this with the heat in saturated steam at 2 pounds 
gage, we have 100 X 40169.5 -^ (34 X 1152.8) = 102 per cent. 

Case four. — Pump exhausts are sometimes led into the 
supply and used for heating purposes along with the engine 
exhausts. If siich conditions be found, what is the heating 
value of such steam? Assume the live steam to enter the 
steam cylinder of the pump under the same pressure and 
quality as recorded for the high speed engine. The steam 
is cut off at about % of the stroke and expands to the end 
of the stroke. With this small expansion the absolute 
pressure at the end of the stroke will be approximately 
% X 112 = 98 pounds, and if enoug^h heat is absorbed from 
the cylinder wall to bring the steam up to saturation at 
the release pressure, we will have a total heat above 32 
degrees, in the exhaust steam per pound of steam at 98 
pounds absolute, of 1186 B. t. u. Comparing- this Avith a 
pound of saturated steam at 2 pounds gage, we have 
100 X 1186 ~ 1152.8 = 103 per cent. Under the conditions 
such as here stated with a high release pressure, a small 
expansion of steam in the cylinder and dry steam at the 
end of the stroke, it is possible to suddenly drop the pressure 
from pump release to a low pressure, say 2 pounds gag-e, 
and have all the steam brought to a state approaching- 
superheat. It is not likely, however, that the steam is dry 
at the end of the stroke in any pump exhaust, because the 
heat lost in radiation and in doing work in the slow moving 
pump would be such as to have a considerable amount of 
entrained water with the steam, thus lowering the quality 
of the steam. These above conditions are extreme and are 
not obtained in practice. 

From cases one and two it would appear that the 
greatest amount of heat that can be expected from engine 
exhausts, for use in heating systems at or near the pres- 
sure of the atmosphere, is 90 to 94 per cent, of that of 



DISTRICT HEATING 295 

saturated, steam at the same pressure. The percentage will, 
in most cases, drop much below this value. All things con- 
sidered, exhaust steam having 80 to 85 per cent, of the value of 
saturated steam at the same pressure is protahly the safest rating 
iDhen calculating the amount of radiation tvhich can he supplied by 
the engines. In many cases no doubt this could be exceeded, 
but it is always best to take a safe value. On the other hand, 
when figuring the amount of condenser tuhe surface or reheater tuhe 
surface to condense the steam, it would he hest to take exhaust steam 
at 100 per cent, cjuality, since this would be working toward 
the side of safety. 

In plants where the exhaust steam is used for heating 
purposes and where the amount supplied by direct acting 
steam pumps is large compared with that supplied by the 
power units, it is possible to have the quality of the ex- 
hausts anywhere between 800 and 1000 B. t. u. per pound 
of exhaust. It should be understood that saturated steam 
at any stated pressure always has the same number of 
B. t. u. in it, no matter whether it is taken directly from 
the boiler, or from the engine exhaust. A pound of the 
mixture of steam and entrained water, taken from engine 
exhausts, should not be considered as a pound of steam. 
If we are speaking of a pound of exhaust steam without 
the entrained water as compared with a pound of saturated 
steam at the same pressure, they are the same, but a pound 
of engine exhaust or mixture is a different thing. 

HOT WATER SYSTEMS. 

165. Four General Classiiioations of hot water heating 
may be found in current work, two applying to the conduit 
piping system and two to the power plant piping system. 
The first, known as the one-pipe com.plete circuit system, is shown 
in Fig. 165. It will be noticed that the water leaves the 
power plant and makes a complete circuit of the district, 
as A, B, C, D, E, F, G, through a single pipe of uniform 
diameter. Prom this main are taken branch mains and 
leads to the various houses, as a, 6, c and d, e, each one 
returning to the principal main after having made its own 
minor circuit. The second is known as the tico-pipe high 
pressure system, in which two main pipes of like diameter 
laid side by side in the same conduit, radiate from the power 
plant to the farthest point on the line reducing in size at 
certain points to suit the capacity of that part of the district 



296 



HEATING AND VENTILATION 



served. This system is represented by Fig-. 166. In the 
one-pipe system the circulation in the various residences is 
maintained, in part, by what is known as the shunt system, 
and in part, by the natural gravity circulation. The circu- 
lation in the two-pipe system is maintained by a high 
differential pressure between the main and the return at 
the same point of the conduit. The force producing move- 
ment of the water in the shunt system is, therefore, very 
much less than in the two-pipe system. As a consequence. 




Power house 



Fig. 165. 
the one-pipe system has a lower velocity of the water in the 
houses and larger service pipes than the two-pipe system. 

In many cases it is desired to connect central heating 
mains to the low pressure hot water systems in private 
plants. Such connections may easily be made with either 
one of the two systems by installing some minor pieces 
of apparatus for controlling the supply. 

The third and fourth classifications, the open and closed 
systems, have about the same meaning as when applied to 
gravity work in isolated plants. The first is open to the 
atmosphere at some point along the circulating, system, 
usually at the expansion tank which is placed on the return 
line just before the circulating pumps. The closed system 
presupposes some form of regulation for controlling exces- 
sive or deficient pressures without the aid of an expansion 
tank. In such cases pumps with automatic control may be 
used for taking care of the reserve supply of water. In the 



DISTRICT HEATING 



297 



open system the exhaust steam may be injected directly into 
the return circulating- water by the use of an open heater 
or a com-ming-ler. The open heater and com-mingler cannot 
be used on the pressure side of the pumps. Surface con- 
densers or reheaters, heating- boilers and economizers may 
be used on either open or closed systems. 



I IE 



,ra 



i 




r 

u 


—r 



e^ 



n 



POWE-R HoU&t 

Fig. 166. 
166. Amount of W^ater Needed per Hour as a Heating 
Medium: — All calculations must necessarily begin with the 
heat lost at the residence. Referring to the living room, 
Table XX, the heat loss is 15267 B. t. u. per hour, requiring 
91 square feet of hot water heating- surface to heat the 
room. Let the circulating water have the following temper- 
atures: leaving the power plant 180°, entering the radiator 
177°, leaving the radiator 157°, and entering the power 
plant 155°. According to these figures, which may be con- 
sidered fair average values, the water gives off to the 
radiator 20 B. t. u. per pound or 166.6 B. t. u. per gallon, thus 
requiring 15267 ~ 166.6 = 91 gallons of water per hour to 
maintain the room at a temperature of 70°. From this a 
safe estimate may be given for design, aUow one gallon of 
water per hour for each square foot of hot vxvter heating surface in 
the district. In a plant operating under high efEiciency this 
may be reduced to 6 pounds per square foot per hour. It is 
very certain that some plants are designed to supply less 
than one gallon, but in such cases it requires a higher tem- 



298 HEATING AND VENTILATION 

perature of the circulating- water and allows little chance 
for future expansion of the plant. A drop of 20 degrees, 
i. e., 20 B. t. u. heat loss per pound of water passing- throug-h 
the radiator, is probably the most satisfactory basis. All 
thing-s considered, the above italicised statement will satisfy 
every condition. (See Art. 173). Having- the total number 
of square feet of radiation in the district, the total amount 
of water circulated throug-h the mains per hour can be 
obtained, after which the size of the pumps in the power 
plant may be estimated. 

167. Radiation in the District; — The amount of radia- 
tion that may be installed in the district is problematical. In 
an averag-e residence or business district the following- flg-- 
ures may easily be realized: 'business Mock, 9000 square feet; 
residence Mode, JfoOO square feet. In certain locations these flg-- 
ures may be exceeded and in others they may be reduced. 
Where the needs of the district are thoroug-hly understood a 
more careful estimate can easily be made. It is always well 
to make the first estimate a safe one and any possible in- 
crease above this fig-ure could be taken care of as in Art. 
166. Referring- to Fig-. 162, an estimate of the amount of 
radiation that may be expected in this typical case, if we 
assume ten business blocks and twenty-one residence blocks, 
is 184500 square feet. This will call for the circulation of 
184.500 gallons of water per hour. 

16S. Future Increase in Radiation: — Prom the tempera- 
tures g-iven in Art. 166, it will be seen that each pound of 
water takes on 25 B. t. u. at the power plant and that there 
is a possible increase of 212 — 180 = 32 B. t. u. per pound 
that may be given to it, thus increasing- the capacity of the 
system approximately 125 per cent. It would not be safe to 
count on such an increase in the averag-e plant because of a 
defective layout in the piping- system or because of a low 
efficiency in some of the pumps or other apparatus in the 
plant. If, however, a plant is installed according- to the 
above figures, the capacity may be quite materially increased 
by increasing- the temperature of the outg-oing- water at the 
plant to 212°. 

169. The Pressure of the \¥ater in the Mains: — The ele- 
vation above the plant at which a central station can supply 
radiation is limited. Water at 180° will weig-h 60.55 pounds 



DISTRICT HEATING 299 

per cubic foot, and the pressure caused by an elevation of 1 
foot is .42 pound per square inch. From this the static pres- 
sure at the power plant, due to a hydraulic head of 100 feet, 
is 42 pounds per square inch. This value should not be ex- 
ceeded, and g-enerally, because of the influence it has on the 
machines and pipes toward producing- leaks or complete 
ruptures, a less head than this is desirable. A static pres- 
sure of 42 pounds may be expected to produce, in a well de- 
signed plant, an outflow pressure of 65 to 75 pounds per 
square inch and a return pressure of 15 to 20 pounds per 
square inch, when working- under fairly heavy service. In 
any case where the mains are too small to supply the radia- 
tion in the system properly, we may expect the value given 
for the outflow to increase and that for the return to de- 
crease. A safe set of conditions to follow is: head, in feet, 
60; static pressure, in pounds per square inch, 25; outgoing 
pressure at the pumps, in pounds per square inch, 50; return 
pressure at the pumps, in pounds per square inch, 5. This 
differential pressure of 45 pounds is caused by the friction 
losses in the piping system, pumps and heaters. Long pipe 
systems, as these are called, have much greater friction losses 
in the long- runs of piping than in the ells, tees, valves, etc., 
hence, the friction head of the pipes is all that is usually 
considered. Where the minor losses are thought to be large, 
they may be accounted for by adding to the pipe loss a 
certain percentage of itself, say 10 to 20 per cent. Pump 
power is figured from the differential pressure. 

The maximum and minimum pressures in the system are 
due to two causes: first, the static head, and second, the 
frictional resistances. These extremes of pressure are ap- 
proximately — static head plus {or minus) one-half the frictional 
resistances. To obtain the frictional resistances, Chezy's 
Equation 95, is recommended. See Merriman's "A Treatise 
on Hydraulics," Arts. 86 and 100, and Church's "Mechanics 
of Engineering," Art. 519. 

4(/,? v" 

hf = X — (93) 

d 2(7 

where Jif = feet of head lost in friction, = friction factor 
(synonymous with coefficient of friction. For clean cast 
iron pipes with a velocity of 5 to 6 feet per second this 
has been found to vary from .0065 to .0048 for diameters 
between .3 and 15 inches respectively. .005 is suggested as 



300 HEATING AND VENTILATION 

a safe average value to use), I = length of pipe in feet, 
V r= velocity of water in feet per second, d = diameter 
of pipe in feet and 2g = 64.4. 

Application. — In Fig-. 166, let it be desired to find the 
differential pressure at the pumps due to the friction losses 
in the line A, B, C, D, E. The lengths of the various parts 
are: power plant to A, 200 feet; A to B, 500 feet; B to C, 
1500 feet; C to D, 1500 feet; and D to E, 500 feet. Assume, 
for illustration, that the total radiation in square feet 
beyond each of these points is: power plant, 125000; A, 85000; 
B, 50000; C, 28000; and D, 12000. This requires 125000, 85000, 
50000, 28000 and 12000 gallons of water per hour, or 4.74, 
3.27, 1.75, 1 and .44 cubic feet of water per second, respec- 
tively, passing- these points. Now, if the velocities be 
roughly taken at 6 and 5 feet per second, (pipes near the 
power plant may be given somewhat higher velocities than 
those at some distance from the plant), the pipes will be 12, 
10, 8, 6 and 4 inches diameter. In applying the equation to 
one part of the line we show the method employed for each. 
Take that part from the power plant to A. With v =: G 

4 X .005 X 200 X 36 

hf = = 2.2 feet. 

64.4 XI 

It should be noted here that Equation 95 refers to pipes 
where all the water that enters at one end passes out the other. 
This is not true in heating- mains where a part of the water 
is drawn of£ at intermediate points. On the other hand, 
Merriman (Art. 99) explains that a water service main, where 
the water is all taken ojf from intermedite tappings and where 
the velocity at the far end is zero, causes only one-third of the 
friction given by the above equation. The case under con- 
sideration falls somewhere between these two extremes, the 
part next the power plant approaching the former and the 
last part of the line exactly meeting- the conditions of the 
latter. Assuming- the mean of these two conditions, which 
is probably very close to the actual, gives two-thirds of that 
found by the equation. Now since this is a double main 
system, i. e., main and return of the same size, the friction 
head for the two lines becomes 2.94 feet, from the power 
plant to A. In a similar way the other parts may be tried 
and the results from the entire line assembled in convenient 
form as in Table XXXVII. 



DISTRICT HEATING 



301 



TABLE XXXVII. 



Distance between points 

Radiation supplied 

Volume of water passing 

point in cu. ft. per sec 

Velocity f. p. s 

Area of pipe sq. ft 

Diam. of pipe in ft 

Tif by (73) for flow main.... 

hf (taking % value) 

fif (% val. flow and return) 



P.P. 


AtoB 


Bto C 


CtoD 


to A. 








200 


500 


150O 


1.500 


12.5000 


85000 


50000 


280OO 


4.74 


3.27 


1.75 


1. 


6 


6 


5 


5 


.79 


.545 


.35 


.20 


1 


.83 


.66 


.5 


2.2 


6.7 


17.4 


23.3 


1.47 


4.47 


11.6 


15.5 


2.94 


8.94 


23.2 


31.0 



DtoE 



500 
12000 



.087 



11.7 

7.8 

15.6 



From the last line of the table obtain the total friction 
head for both mains, not including- ells, tees, valves, etc., 
to be 81.6 feet. This is equivalent to 34.3 pounds per square 
inch. Allowing- 20 per cent, of all the line losses to cover 
the minor losses we have approximately 40 pounds differen- 
tial pressure, which is a reasonable value. 



Another approximate method of analyzing this problem is to 
assume the amount of water passing any run of main to be 
the total requirement beyond the run plus one-half of that 
amount taken off through the tappings along- the run and 
estimate the friction head from this figure. This plan will 
call for the full value of Equation 95 and not the two-thirds 
value as before. As an illustration, allowing one gallon of 
water per square foot of radiation per hour, approximately 
125000 gallons pass from P. P. to A. Some of this is taken 
off in tappings and the rest of 40000 is taken off through the 
branch main. 85000 pass A and 35000 are taken off through 
the tappings to B. 50000 pass B and 22000 are taken off 
through tappings to C. 28000 pass O and 16000 are taken off 
to D. 12000 pass D and all are taken through tappings to E, 
the end of the line. 

The amount of water chargeable to each run will be: 
P. P. to A, 125000, A to B, 50000 + 35G00 ^ 2 = 67500, B to C, 
28000 + 22000 -f- 2 = 39000, C to D, 12000 + 16000 4- 2 = 
20000, and from D to E, 12000 -4- 2 = 6000 gallons per hour. 
Reduced to cu. ft. per sec. this is P. P. to A, 4.7, A to B, 2.5, 
B to C, 1.44, C to D, .74, and D to E, .44. 



302 HEATING AND VENTILATION 

For purpose of comparing with preceding method, vol- 
umes, velocities, pipe sizes (the same as in Table XXXVII) 
and friction heads are shown in Table XXXVIII. 



TABLE XXXVIII. 



Volume passing- through section 
cu. ft. per sec. 

Average velocity in f . p. s 

Area of pipe in sq. ft 

Diam. of pipe in ft. 

hf by (95) flow and return 



PPto 
A 


AtoB 


Bto C 


OtoD 


4.7 


2. .5 


1.44 


.74 


6 


4.6 


4.1 


3.7 


.79 


.54.5 


.35 


.20 


1 


.83 


.66 


.5 


4.4 


2.34 


23.6 


25.6 



DtoE 



5. 
.087 
..33 
23.4 



Total friction head = 79. 34 ft. not including ells, tees, valves, etc. 

170. Velocity of the Water in the Mains and the Dia- 
metei' of the Mains: — The district is first chosen and the 
layout of the conduit system is made. This is done inde- 
pendently of the sizes of the pipes. When this layout is 
finally completed, the pipe sizes are roughly calculated for 
all the important points in the system and are tabulated 
in connection w^ith the friction losses for these parts, as 
in Art. 169. When this is done. Equation 96, which is rec- 
ommended to be used in connection with Equation 95, may be 
applied and the theoretical diameters found. (The approxi- 
mate diameters and the friction heads need not be calcu- 
lated in Equation 95 for use in Equation 96, providing- some 
estimate may be made for the value of 7ir, for the various 
lengths of pipe. If desired, hf may be assumed without any 
reference to the diameter, but this is a rather tedious proc- 
ess. F6r discussion of this point see Church's Hydraulic 
Motors, Arts. 121-124 b.) 



.629 % X 



(96) 



where d, hf, and I are the same as in Equation 95, and Q = 
cubic feet of water passing through the pipe per second. 
This equation differs from those given in the references 
stated, in that the term % is inserted as a mean value be- 
tween the two extreme conditions, as stated in Art. 169. 



DISTRICT HEATING 303 

Application. — Let it be desired to find the diameter for 
the single main between the power plant and A, Art. 169, 
with hf = 1.47 



r 2 X .005 X 200 X (4.74)= n 1/5 

z:r 1 f t. 

L S V 1.47 J 



Applj'ing- to the entire line with hf as given in next to last 
line of Table XXXVII, gives power plant to A, d — 12 inches; 
-4. to B, a — 10 inches; B to C, a — 8 inches; C \o B, a — 6 
inches; and D to E, d = 4 inches. 

In some cases, when close estimating is not required, 
it is satisfactory to assume a velocity of the water and find 
the diameter without considering the friction loss. In many 
cases, however, this would soon prove a positive loss to the 
company. With a low velocity, the first cost would be large 
and the operating cost would be low. On the other hand, 
if the velocity Avere high, the first cost would be small and 
the operating cost and depreciation would be large. As an 
illustration of how the friction head increases in a pipe of 
this kind with increased velocity, refer to the run of mains 
between B and C. Assuming a velocity of 10 feet per 
second, which in this case would be very high, the friction 
head, hf, for the single main, becomes 62 and the theoretical 
diameter is 5.5, say 6 inches. The friction head, as will be 
seen, is 5.4 times the corresponding value when the velocity 
was 5 feet per second. Since the pump must work contin- 
ually against this head, it Avould incur a financial loss that 
would soon exceed the extra cost of installing larger pipes. 
It is found in plants that are in first class operation that 
the velocities range from 5 to 7 feet per second. 

The calculations in Arts. 169 and 170 are very much 
simplified by the use of the chart shown in the Appendix. 
In planning a system of this kind, find the friction head 
on the pumps and the diameters of the pipes for various 
velocities, say 4, 6, 8 and 10 feet per second. Estimate the 
probable first cost and the depreciation of the conduit sys- 
tem for each velocity, and balance these figures with the 
operating cost for a period of, say five years, to see which is 
the most economical velocity to use in figuring the system. 

171. Service Connections are usually installed from 30 
to 36 inches below the surface of the ground, and are in- 
sulated in some form of box conduit which compares favor- 
ably with that of the main conduit. Service branches are 



304 HEATING AND VENTILATION 

1^/4-, 1^/4- and 2-inch wroug-ht iron pipe. These are usually 
carried to the building- from the conduit at the expense of 
the consumer. Such branch conduits are not drained by- 
tile drains. 

172. Total Steam Available and B. t. u. I-iberated per 
Hour for Heating the Circulating "Water: — The amount of 
steam available for heating- the circulating- water is that 
g-iven off by the g-enerating- units, plus that from the cir- 
culating- pumps, plus that from the city water supply pumps 
if there be any, plus that from the auxiliary steam units 
in the plant, i. e., small pumps, eng-ines, etc. In the typical 
application this amounts to 23100 + 12720 + 8680 = 44500 
pounds per hour. 

This steam, of course, is not equal to g-ood dry steam in 
heating- value because of the work it has done in the engine 
and pump cylinders, but a g-ood estimate of its value may 
be approximated. In addition to the terms used in Equation 
93, let q' = heat in the returning- condensation per pound; 
then the heat available for heating- purposes per pound of 
exhaust steam is 

B. t. u. = w r -\- q — q' (97) 

It is probably safe to consider the quality of the steam as 
85 per cent, of that of g-ood dry steam at the same pressure. 
Since the pressure of the exhaust from a non-condensing- 
eng-ine, as it enters the heater, is near that of the atmos- 
phere, and since the returning- condensation is at a tempera- 
ture of about 180°, the total amount of heat g-iven off from 
a pound of exhaust steam to the circulating- water is 
.85 X 970.4 + 180 — (180 — 32) = 856.84, say 850. If Ws = 
pounds of exhaust steam available, the total number of 
B. t. u. g-iven off from the exhaust steam per hour is 

Total B. t. u. = 850 Ws (98) 

Applying- this to the typical power plant g-ives 850 X 
44500 =: 37825000 B. t. u. per hour. This amount is probably 
a maximum under the conditions of lig-hting- units as stated, 
and would be true for only 5 hours out of 24. At other 
times the exhaust steam drops off from the lig-hting- units 
and this deficiency must be made g-ood by heating- the circu- 
lating- water directly from the coal, by passing- the water 
throug-h heating- boilers or by passing- it throug-h economiz- 
ers where it is heated by the waste heat from the stack 
g-ases. 



DISTRICT HEATING 305 

173. Amount of Hot Water Radiation in the District 
that can be Supplied by One Pound of Exhaust Steam on a 
Zero Day: — In Art. 166, each pound of water takes on 25 
B. t. u. in passing- through the reheaters at the power plant, 
and gives off at least 20 B. t. u. in passing through the 
radiator. The number of pounds of water heated per pound 
of steam per hour is, Ww = (Total B. t. u. available per 
pound of exhaust steam per hour) -^ 25, and the total radia- 
tion supplied is 



Total B. t. u. available per lb. of exhaust steam per hr. 

R,c = (99) 

8.33 X 25 



which for average practice reduces to 



850 

• = 4 square feet approx. (100) 

208 



Applying Equation 99 for the five hour period when the 
exhaust steam is maximum gives Rw = 37825000 -=- 208 = 
181851 square feet. It is not safe to figure on the peak load 
conditions. It is better to assume that for half the time, 
35000 pounds of steam are available and will heat 35000 X 
4 =: 140000 square feet of radiation. 



174. The Amount of Circulating Water Passed through 
the Heater Necessary to Condense One Pound of Exhaust 
Steam is 

Total B. t. u. available per lb. of exhaust steam per hr. 

Ww = (101) 

25 



With the value given above for the exhaust steam this be- 
comes, for 100 and 85 per cent, respectively, 



1000 

Ww = = 40 pounds (102) 

25 



850 

Ww = = 34 pounds (103) 

25 



306 HEATING AND VENTILATION 

175. Amount of Hot Water Radiation in the District 
tiiat can be Heated by One Horse-PoAver of E^xhaust Steam 
from a Non-Condensing Engine on a Zero Day: — 

Rw = 4 X (pounds of steam per H. P. hour) (104) 
This reduces for the various types of engines, as follows: 



Simple hig-h speed 


4 X 


34 = 136 


square feet 


" medium " 


4 X 


30 = 120 




Corliss 


4 X 


26 = 104 




Compound high " 


4 X 


26 = 104 




" medium " 


4 X 


25 = 100 




" Corliss 


4 X 


22 = 88 





176. Amount of Radiation that can be Supplied by Kx- 
haust Steam in Equations 99 and 100 at any other Temper- 
ature of the l^^ater, tw, than that Stated, ^vith the Room\ 
Temperature, f. Remaining,- the Same: — The amount of heat 
passing- through one square foot of the radiator to the room 
is in proportion to ttv — f. In Equations 99 and 100, tw — f = 
100. Now if ^«> be increased x degrees, so that tiv — f = 
(100 + X) then each square foot of radiation in the building 

100 + a? 

will give off times more heat than before and 

100 

each pound of exhaust steam will supply only 

4 X 100 

Rw ■= square feet (105) 

100 + X 

This for an increase of 30 degrees, which is probably a max- 
imum, is 

4 

Rw = = 3 square feet (106) 

1.3 

Compared with Equation 100, Equation 105 shows, with a 
high temperature of the water entering the radiator, that 
less radiation is necessar3r to heat any one room and that 
each square foot of surface becomes more nearly the value 
of an equal amount of steam heating surface. Calculations 
for radiation, however, are seldom made from high tempera- 
tures of the water, and this article should be considered an 
exceptional case. 

177. Elxhaust Steam Condenser (Reheater), for Reheat- 
ing the Circulating Water: — In the layout of any plant 
the reheaters should be located close to the circulating 



DISTRICT HEATING 



307 



pumps on the hig-h pressure side. They are usually of the 
surface condenser type (Fig-. 167) and may or may not be 
installed in duplicate. Of the two types shown in the fig-- 
ure, the water tube type is probably the more common. The 
same principles hold for each in desig-n. In ordinary heaters 
for feed water service, wroug-ht iron tubes of 1%- to 2-inches 



/ 

(r 

lujj 



LAri 

CI 



WATtR 
M 

bl 1 Id 



B" 



WATER STtAM DRIP 

WATtR-TUBL TYPt 



■^s 



Fig-. 167. 



WATER 



WATLR STEAM 
DRIP 

STEAM-TUBt TYPE 



diameter are g-enerally used, but for condenser work and 
where a rapid heat transmission is desired, brass or copper 
tubes are used, having- diameters of %- to 1-inch. In heating- 
the circulating- water for district service, the reheater is 
doing- very much the same work as if used on the condens- 
ing- system for eng-ines or turbines. The chief difference is 
in the pressures carried on the steam side, the reheater con- 
densing- the steam near atmospheric pressure and the con- 
denser carrying about .9 of a perfect vacuum. In either case 
it should be piped on the water side for water inlet and out- 
let, while the steam side should be connected to the exhaust 
line from the engines and pumps, and should have proper 
drip connection to draw the water of condensation off to a 
condenser pump. This condenser pump usually delivers the 
water of condensation to a storag-e tank for use as boiler 
feed, or for use. in making- up the supply in the heating- 
system. 

In determining- the details of the condenser the follow- 
ing- important points should be investigated: the amount of 
heating- surface in the tubes, the size of the water inlet and 
outlet, the size of the pipe for the steam connection, the size 
of the pipe for the water of condensation and the length 
and cross section of the heater. 



178. Amount of Heating: Surface in the Reheater Tubes: 

-The general equation for calculating the heating surface in 



308 HEATING AND VENTILATION 

the tubes of a reheater (assuming- all heating- surface on 
tubes only), is 

Total B. t. u. given up by the exhaust steam per hr. 

Rt = (107) 

K (Temp. diff. between inside and outside of tubes) 

The maximum heat given off from one pound of exhaust 
steam in condensing at atmospheric pressure is 1000 B. t. u., 
the average temperature difference is approximately 47 
degrees, and K may be taken 427 B. t. u. per degree dif- 
ference per hour. In determining K, it is not an easy mat- 
ter to obtain a value that will be true for average practice. 
Carpenter's H. & V. B. Art. 47 quotes the above figure for 
tests upon clean tubes, and volumes of water less than 
1000 pounds per square foot of heating surface per hour. 
It is found, however, that the average heater or condenser 
tube with its lime and mud deposit will reduce the efficiency 
as low as 40 to 50 per cent, of the maximum transmission. 
Assume this value to be 45 per cent.; then if Ws is the 
number of pounds available exhaust steam. Equation 107 
becomes 

1000 Ws 1000 Ws 1000 Ws Ws 

Et = = = = (108) 

K(ts — tiv) 427 X .45 X 47 9031 9.1 

In "Steam Engine Design," by Whitham, page 283, the 
following equation is given for surface condensers used on 
shipboard: 

W L 

~ cE (Ti — t) 

where S = tube surface, W = total pounds of exha,ust steam 
to be condensed per hourj L = latent heat of saturated steam 
at a temperature Ti, K = theoretical transmission of B. t. u. 
per hour through one square foot of surface per degree dif- 
ference of temperature = 556.8 for brass, c = efficiency of 
the condensing surface = .323 (quoted from Isherwood), T^ = 
temperature of saturated steam in the condensers, and t = 
average temperature of the circulating- water. 

With L = 970.4, c = .323, K = 556.8 and Ti — t = 47, we 
may state the equation in terms of our text as 

970.4 Ws 970.4 Ws Ws 

Rt = = = (109) 

.323 X 556.8 X 47 8446 8.7 

In Sutcliffe "Steam Power and Mill Work," page 512, the 
author states that condenser tubes in g-ood condition and set 



DISTRICT HEATING 309 

in the ordinary way have a condensing- power equivalent to 
13000 B. t. u. per square foot per hour, when the condensing 
water is supplied at 60 deg-rees and rises to 95 degrees at dis- 
charge, although the author gives his opinion that a trans- 
mission of 10000 B. t. u. per square foot per hour is all that 
should be expected. This checks closely with Equation 108, 
which gives the rate of transmission 9031 B. t. u. per square 
foot per hour. 

The following empirical equation for the amount of heat- 
ing- surface in a heater is sometimes used: 

Rt = .0944 Ws (110) 

where the terms are the same as before. 

Application. — Let the total amount of exhaust steam 
available for heating the circulating water be 35000 pounds 
per hour, the pressure of the steam in the condenser be 
atmospheric and the water of condensation be returned at 
180°; also, let the circulating- water enter at 155° and be 
heated to 180°. These values are good average conditions. 
The assumption that the pressure within the condenser is 
atmospheric might not be fulfilled in every case, but can be 
approached very closely. From these assumptions find the 
square feet of surface in the tubes. 



Equation 108, 


Rt 


= 


35000 

= 3846 sq. ft. 

9.1 


Equation 109, 


Rt 


= 


35000 

Af\00 ^ri ft 


— iv^o sq. It. 
8.7 


Equation 110, 


Rt 


= 


35000 X .0944 = 3304 sq. ft. 


Sutclifee 


Rt 


^ 


1000 X 35000 
= 3500 sq. ft. 



10000 

If 3846 square feet be the accepted value it will call for 
three heaters having 1282 square feet of tube surface each. 

179. Amount of Reheater Tube Surface per Bngrine 
Horse-Power: — Let ws be the pounds of steam used per 
I. H. P. of the engine; then from Equation 108 

Ws 

Rt (per /. E. P.) = (111) 

9.1 



310 HEATING AND VENTILATION 

This reduces for the various types of engines as follows: 



Simple high speed 


34 - 


- 9.1 = 3.74 


square feet 


medium " 


30 - 


- 9.1 = 3.30 




Corliss 


26 - 


- 9.1 = 2.86 




Compound high " 


26 - 


- 9.1 = 2.86 




medium " 


25 - 


- 9.1 = 2.75 




Corliss 


22 - 


- 9.1 = 2.42 





180. Amount of Hot Water Radiation in the District 

that can he Supplied hy One Square Foot of Reheater Tuhe 

Surface: — If the transmission through one square foot of 

tube surface be K (ts — tw) =. 9031 B. t. u. per hour and the 

amount of heat needed per square foot of radiation per 

hour = 8.33 x 25 = 208, as given in Eqaution 99, then 

9031 

Rw (per sq. ft. of tube surface) = = 43.4 sq. ft. (112) 

208 

181. Some Important Reheater Details: — Inlet and outlet 
pipes. — Having three heaters in the plant, it seems reason- 
able that each heater should be prepared for at least one- 
third of the water credited to the exhaust steam. Prom 
Art. 173 this is 140000 -H 3 = 46667 gallons = 10800000 cubic 
inches per hour. The velocity of the water entering and 
leaving the heater may vary a great deal, but good values 
for calculations may be taken between 5 and 7 feet per 
second. Assuming the first value given, we have the area 
of the pipe = 10800000 -^ (5 X 12 X 3600) = 50 square inches, 
and the diameter 8 inches. 

The size of the reheater shell. — Concerning the velocity of 
the water in the reheater itself, there may be differences of 
opinion; 100 feet per minute will be a good value to use 
unless this value makes the length of the tube too great for 
its diameter. If this is the case the tube will bend from 
expansion and from its own weight. At this velocity the 
free cross sectional area of the tubes, assuming the water 
to pass through the tubes as in Fig. 167, will be 150 square 
inches. If the tubes be taken % inch outside diameter, 
with a thickness of 17 B. W. G., and arranged as usual in 
such work, it will require about 475 tubes and a shell diam- 
eter of approximately 30 inches. If the inner surface of the 
tube be taken as a measurement .of the heating surface and 



DISTRICT HEATING 311 

the total surface be 1282 square feet, the length of the re- 
heater tubes will be approximately 16 feet. 

The ratio of the leng-th of the tube to the diameter is, 
in this case, 256, about twice as much as the maximum ratio 
used by some manufacturers. It will be better, therefore, 
to increase the number of tubes and decrease the length. 
With a velocity of the water of 50 feet per minute, the 
values will be approximately as follows: free cross sec- 
tional area of the tubes, 300 square inches; number of tubes, 
950; diameter of shell, 40 inches; length of tubes, 8 feet. 
These values check fairly well and could be used. 

The size of exhaust steam connection.- — To calculate this, use 

the equation 

144 Qs 

A = (113) 

V 

where Qs = volume of steam in cubic feet per minute, V = 
velocity in feet per minute, and A = area of pipe in square 
inches. When applied to the reheater using 35000 pounds 
of steam per hour, at 26 cubic feet per pound and at a veloc- 
ity through the exhaust pipe of 6000 feet per minute, it gives 

144 X 35000 X 26 

J. = = 360 sq. in. = 22 in. dia. 

60 X 6000 

Try also, from Carpenter's H. & V. B., page 284 

d = V (114) 

1.23 

Allowing 30 poiinds of steam per H. P. hour for non-condens- 
ing engines we have 35000 -^ 30 rr 1166 horse-power; then 
applying the above we obtain d = 16 inches. Comparing 
the two Equations, 113 and 114, the first will probably admit 
of a more general application. The velocity 6000 for exhaust 
steam may be increased to 8000 for very large pipes and 
should be reduced to 4000 for small pipes. In the above 
applications a 20 inch pipe will suffice. 

The return pipe for condensation. — The diameter of the pipe 
leading to the condenser pump will naturally be taken from 
the catalog size of the pump installed. This pump would 
be selected from capacities as guaranteed by the respective 
manufacturers and should easily be capable of handling the 
amount of water that is condensed per hour. 

The value of a high pressure steam connection. — If desired, 
the reheater may also be provided with a high pressure 



312 HEATING AND VENTILATION 

steam connection, to be used when the exhaust steam is not 
sufficient. This steam is then used throug-h a pressure-re- 
ducing- valve which admits the steam at pressures varying 
from atmospheric to 5 pounds g^ag-e. There is some question 
concerning the advisability of doing this. Some prefer to 
install a high pressure steam heater, as in Art. 182, to be 
used independently of the exhaust steam heaters. This 
removes all possibility of having excessive back pressure 
on the engine piston, as is sometimes the case where high 
pressure steam is admitted with the exhaust steam. 

It has been the experience of some who have operated 
such plants that where more heat is needed than can be 
supplied by the exhaust steam, it is better to resort to heat- 
ing boilers and economizers ,than to use high pressure steam 
for heating. 

182. Hi^h Pressure Steam Heater: — When this heater is 
used it is located above the boiler so that all the condensa- 




tion freely drains back to the boilers by gravity as in Fig. 
168. In calculating the tube surface, use Equation 107 with 



DISTRICT HEATING 313 

the full value of the steam and the steam temperatures 
chang-ed to suit the increased pressure. Such a heater as 
this gives good results. 

183. Circulating Pumps: — Two types of pumps are in 
general use: centrifugal and reciprocating. Each type is 
somewhat limited in its operation. The centrifugal pump 
has difficulty in operating against high heads and the recip- 
rocating pump is very noisy when running at a high piston 
speed. Since each type is in successful operation in many 
plants, no comparisons will be made between them further 
than to say that the former, being operated by a steam en- 
gine, may be run more economically than the latter because 
of the possibilities of using the steam expansively. It will 
be noted, however, that this same steam is to be used in the 
exhaust steam heaters for warming the circulating water 
and hence there would be little, if any, direct loss from this 
source in the use of the reciprocating pump. 

Having given the maximum- amount of water to be 
circulated per hour, consult trade catalogs and select the 
number of pumps and the size of each pump to be installed. 
The sizes of the pumps can easily be determined when the 
number of them has been decided upon. This latter point 
is one upon which a difference of opinion will probably be 
found. No exact rule can be applied. In a plant of, say 
not more than 150000 square feet of radiation (150000 gal- 
lons of water per hour, or 3 million gallons for twenty-four 
hours), some designers would put in three pumps, each 
having 1.5 million gallons capacity; in which case one pump 
could be cut out for repairs and the other two would be 
able to care for the service temporarily. Other designers 
would use four pumps at about one million gallons each. 
The fewer the pumps installed, in any case, the greater 
should be the capacity of each. The following values will 
be found fairly satisfactory: 

1 Pump. Cap. = (1 to 1.25) times max. requirem't of system 

2 Pumps. " (each) — .75 

3 Pumps. " " = .5 " " " " " 

4 Pumps. " " = .3 " " " " " 

Having given the capacity of each pump in gallons of 
water per minute, the size, the horse-power and the steam 
consumption of each pump can be calculated. In obtaining 
the size of the pump it will be necessary to know the speed, 



314 HEATING AND VENTILATION 

y, of the piston in feet per minute, the strokes, N, per minute 
and the per cent, of sliij, s (100 per cent. — S, where fif = hy- 
draulic efficiency). The speed varies between 100, for small 
pumps, and 75, for large pumps. The strokes vary between 
200, for small pumps, and 40, for large pumps, and the slip 
varies between 5 and 40 per cent., depending- upon the fit of 
the piston and the valves. In pumps that have been in serv- 
ice for some time the slip will probably average 20 per cent. 
The cross sectional area of the water cylinder in square 
inches is 

cubic inches pumped per minute 

W. C. A. = (:15) 

8 X V X 12 

from which we may obtain the diameter of the water cyl- 
inder. 

The steam cylinder area is usually figured as a certain 
ratio to that of the water cylinder area, as 

S. C. A. = (1.5 to 2.5) X W. C. A (116) 

from which we may obtain the diameter of the steam cylin- 
der. 

The length of the stroke, L, in inches, may be obtained 
from the speed and the number of strokes such that 

12 y 
L = (117) 

N 

All direct acting steam pumps are designated by diam- 
eter of steam cylinder X diameter of water cylinder X length 
of stroke, as 

14" X 12" X 18" 

Duplex pumps have twice the capacity of single pumps 
having the same sized cylinders. 

To find the indicated horse-power, 7. H. P., of the pumps, 
reduce the pressure head, p, in pounds per square inch, to 
pressure head in feet, h; multiply this by the pounds of 
water, W, pumped per minute and divide the product by 
33000 times the mechanical efficiency, E. 

W h 

I. H. P. = (118) 

33000 E 

To reduce from pressure head in pounds to pressure 
head in feet, divide the pressure head in pounds by weight 



DISTRICT HEATING 315 

of a column of water one square inch in area and one foot 
higrh. The general equation for this is 

144 p 



w . 
where ic = the weight of a cubic foot of water at the given 
temperature and p = differential pressure in pounds per 
square inch. 

In pump service of this kind the pressure head, j), 
against which the pump is acting, is not the result of the 
static head of water in the system but is due to the inertia 
of the water and to the resistance to the flow of water 
through the piping system and the heaters. This frictional 
resistance inay be calculated as shown in Art. 169. Read 
this part of the work over carefully. 

For an illustration of combined pressure head, p, and 
friction head, hf, see Art. 186 on boiler feed pumps. Having 
found the /. H. P. of any pump, multiply it by the steam con- 
sumption per I. H. P. hour and the result will be the steam 
consumption of tlie pump. This exhaust steam will be con- 
sidered a part of the general supply when figuring the size 
of the exhaust steam heaters in the system. 

The mechanical efficiency, E, of piston pumps depends 
upon the condition of the valves and upon the speed, and 
varies from 90 per cent, in new pumps, to 50 per cent, in 
pumps that are badly worn. A fair average would be 70 
per cent. 

The steam consumption for reciprocating, simple and 
duplex non-condensing pumps would approximate 100 to 
200 pounds of steam per 7. H. P. hour — the greater values re- 
ferring to the slower speeds. 

184. Centrifugal Pumps: — Centrifugal pumps are of 
two classifications, the Volute and the Turbine. The prin- 
ciples upon which each operate are very similar. The ro- 
tating impeller, or rotor, with curved blades draws the 
water in at the center of the pump and delivers it from the 
circumference. The rotor is enclosed by a cast iron case- 
ment which is shaped more or less to fit the curvature of 
the edges of the blades on the rotor. Centrifugal pumps 
are used where large volumes of \vater are required at low 
heads. They are used in city water supply systems, in cen- 
tral station heating sj'stems, in condenser service, in irri- 



316 HEATING AND VENTILATION 

g-ation work and in many other places where the pressure 
head operated against is not excessive. The efficiency of 
the averag-e centrifug^al pump is from 65 to 80 per cent., 
75 per cent, being- not uncommon. In places where such 
pumps are used the .head is usually below 75 feet, although 
some types, when direct connected to high speed motors, 
are capable of operating against heads of several hundred 
feet. 

Some of the advantages of centrifugal pumps over hor- 
izontal reciprocating pumps are: low first cost, simplicity, 
few moving parts, compactness, uniform flow and pressure 
of water, freedom from shock, possibilities of direct connec- 
tion to high speed motors and the ability to handle dirty 
water without injuring the pump. 

One of the advantages of piston pumps over centrifugal 
pumps is the fact that they are more positive in their opera- 
tion and work against higher heads. 

Centrifugal pumps, when connected •to engine and tur- 
bine drives, benefit by the expansion of the steam and are 
much more economical than the direct acting piston pump, 
which takes steam at full pressure for nearly the entire 
stroke. The amount of steam used in the pumps in central 
station work, however, is not a serious factor, since all of 
the heat in the steam that is not used in propelling the 
water through the mains is used in the heaters to increase 
the temperature of the water. 

The sphere of usefulness of the centrifugal pump in 
central station heating is increasing. The direct acting 
piston pump, when operating at fairly high speeds, causes 
h9,mmering and pounding in the transmission lines, and 
these noises are sometimes conveyed to the residences and 
become annoying to the occupants. This feature is not so 
noticeable in the operation of the centrifugal pump. 

Application. — In Art. 167 assume the capacity of the 
plant, 10 business blocks and 21 residence blocks, to require 
184500 gallons of water per hour; the same to be pumped 
against a pressure head (Art. 169) of 50 — 5 pounds, by hori- 
zontal, direct acting piston pumps. Assume also the steam 
consumption of the pumps to be 100 pounds per I. H. P. hour 
and the average temperature of the water at the pumps to 
be (180 + 155) -^ 2 = 167.5 degrees. Apply Equation 118, 
where li ~ calculated total friction head for the longest line 



DISTRICT HEATING 317 

in the system (this is designated by Jif in Art. 169), or where 

p = total difference between the incoming- and the outgoing 

pressures. With the weight of a cubic foot of water at 167.5 

degrees = 60.87 pounds and with p = 45, we have Ji = 106.5 

feet, and the indicated horse-power of the pumps, assuming 

65 per cent, meclianical efficiency, is 

184500 X 8.33 X 106.5 

/. Ef. F. = ■ • = 127.2 

33000 X .65 X 60 

From this the steam consumption will probably be 12720 

pounds per hour. 

If centrifugal pumps were selected the horse-power 
would be calculated from the same equation, but the steam 
consumption of the engine driving it would probably be 30 
to 40 pounds of steam per horse-power. 

1S5. City Water Supply Pumps: — Horizontal, direct act- 
ing duplex pumps for use on city water supply service are 
the same as those used to circulate the water in heating 
systems; hence, the foregoing descriptions apply here. The 
/. H. P. of the city water supply pumps would be calculated 
by use of Equation 118. If the pumps lift the water from the 
wells, as would probably be the case, the suction pressure 
would be negative and would be added to the force pressure. 

Application. — Assume the pressure in the fresh water 
mains 60 pounds and the suction pressure 10 pounds; there- 
fore, p = 60 — ( — 10) = 70 pounds, and with the water at 
65 degrees, h = 144 X 70 -^ 62.5 = 161 feet. These pumps 
are each rated at 1.5 million gallons in 24 hours, and deliver 
62500 X 8.33 = 520833 pounds of water per hour, when run- 
ning at full capacity. Assuming each pump to deliver 75 per 
cent, of the full requirement of the system, the total amount 
of water pumped per hour for the city water supply would 
approximate 520833 -f- .75 = 694444 pounds, and the total 
average horse-power used in pumping the water would be 

694444 X 161 

/. H. F. = = 86.8 

60 X 33000 X .65 

With 100 pounds of steam per horse-power hour, this would 

amount to 8680 pounds of exhaust steam available per hour 

for use in heating the circulating water. 

186. Boiler Feed Pumps: — Horizontal pumps for high 

pressure boiler feeding are selected in a similar way. Such 

units are called auxiliary steam units and, because the steam 



318 HEATING AND VENTILATION 

required is small, they are sometimes piped to a feed water 
heater for heating the boiler feed. The velocity of the water 
through the suction pipe may be taken 200 feet per minute 
and in the delivery pipe 300 feet per minute. The piston 
speed, the strokes per minute and the slip would be very 
much the same as stated under circulating pumps. Such 
pumps should have a pumping capacity about twice as great 
as the actual boiler requirements, and in small plants where 
only one pump is needed, the installation should be in dupli- 
cate. The sizes of the cylinders and the efficiencies are 
about as stated for the larger circulating pumps. 

In determining the horse-power of a boiler feed pump, 
four resistances must be overcome; i. e., pressure head, p, or 
boiler pressure; suction heat, hs; delivery head, ha, and 
the friction head, hf. The first three values are usually 
given. The friction head includes the resistances in all pip- 
ing, ells and valves from the supply to the boiler. The fric- 
tion in the piping may be taken from Table 42, Appendix, or 
it may be w^orked out by Equation 95. The friction in the ells 
and valves is more difficult to determine and is usually stated 
in equivalent length of straight pipe of the same diameter. 
A rough rule used by some in such cases is as follows: "to 
the length of the given pipe, add 60 times the nominal diam- 
eter of the pipe for each ell, and 90 times the diameter for 
each globe valve," then find the friction head as stated 
above. A straight flow gate or water valve could safely be 
taken as an ell. For simplicity of calculation, all of the 
above resistances may be reduced to an equivalent head, 
such that 

(119) 
144 ij 

he — + lX& + lis + lit 

W 

where w = weight of one cubic foot of water at the suc- 
tion temperature, w may be obtained from Table 9, Ap- 
pendix, and lif may be taken from Table 42. The horse-power 
by Equation 118 then becomes, if W r= pounds of water 
pumped per minute, 

W X lio 

I. II. P. — . (120) 

33000 Fj 

Application. — Let p = 125 pounds gage, %o rr 62.5, lui = 8 
feet, 7*6 = 20 feet, horizontal run of pipe from supply to 



DISTRICT HEATING 319 

pump = 20 feet, horizontal run of pipe from pump to boiler = 
30 feet; also, let the pump supply 89000 pounds of water 
per hour to the boiler. This is twice the capacity of the 
boiler plant. With this amount of water at the usual veloc- 
ity it will give a suction pipe of 4.5 inches diameter, and a 
flow pipe of 4 inches diameter. Let there be two ells and 
one gate valve on the suction pipe, and three ells, one globe 
valve and one check valve on the delivery pipe. We then 
have an equivalent of 107 feet of suction pipe, and 158 feet 
of delivery pipe. Referring to Table 42, hf is approximately 
7 feet, and the total head is 

144 X 125 

he = • + 8 + 20 + 7 = 323 feet. 

62.5 

In the use of most boiler feed pumps it is considered 
unnecessary to determine ht so carefully. A verj^ satisfac- 
tory waj^ is to obtain the total head pumped against, exclu- 
sive of the friction head, and add to it 5 to 15 per cent., de- 
pending upon the complications in the circuit. Substituting 
the above in Equation 120, we obtain 

89000 X 323 

/. //. P. = = 22.3 

60 X 33000 X .65 

Work out the value of hf by Equation 95 and see how 
nearly it checks with the above. 

187. Boilers: — A number of boilers will necessarily be 
installed in a plant of this kind, and a good arrangement is 
to have them so piped with water and steam headers that 
any number of the boilers may be used for steaming pur- 
poses and the rest as water heaters. They should also be so 
arranged that any of the boilers may be thrown out of 
service for cleaning or repairs and still carry on the work 
of the plant. By doing this the boiler plant becomes very 
flexible and each boiler is an independent unit. Any good 
water tube boiler would serve the purpose both as a steam- 
ing and as a heating boiler. Where the boilers are used as 
heaters, the water should enter at the bottom and come out 
at the top. Where the water enters at the top and comes 
out at the bottom, the excessive heating of the front row of 
tubes retards the circulation of the water by this heat, and 
produces a rapid circulation through the rear tubes where 
the heat is the least. This rapid circulation in the rear tubes 



320 HEATING AND VENTILATION 

is not a detriment, but it is less needed there than in the 
front ones. It would be decidedly better if the rapid circu- 
lation were in the front row, causing the heat from the fire 
to be carried off more readily, and by this means g-iving less 
dang-er of burning- the tubes. In the latter case the forced 
circulation from the pumps will be aided by the natural cir- 
culation from the heat of the fire, and the life of all the 
tubes becomes more uniform. Fig-. 169 shows a typical 
header arrang-ement. 

Boilers are usually classified as fire tube and water tube. 
Fire tuhe hollers are of the multitubular type, having- the flue 
g-ases passing- throug-h the tubes and water surrounding- 
them. Water tuhe boilers have the water passing- throug-h the 
tubes and the flue gases surrounding them. The heating sur- 
face of a boiler is composed of those boiler plates having the 
heated flue gases on one side and the water on the other. A 
IjoiJer horse-power may be taken as follows: 
Centennial Rating. 

One B. H. P. = 30 pounds of water evaporated from feed 
water at 100° F. to steam at 70 pounds gage pressure. 
A. S. M. E. 

One B. H. P. = 34.5 pounds of water evaporated from 
and at 212° F. 

In laying out a boiler plant some good approximations 
for the essential details are: 

One B. H. P. = 11.5 square feet of heating surface, 
(multitubular type). 

One B. H. P. = 10 square feet of heating surface 
(water tube type). 

One B. H. P. — .33 square foot of grate surface 
(small plant, say one boiler). 

One B. H. P. = .25 square foot of grate surface 
(medium sized plant, say 500 H. P.). 

One B. H. P. = .20 square foot of grate surface 
(large plants). 

Pounds of water evaporated per square foot of heating 
surface per hour = 3 (approx. value). 

188. Square Feet of Hot Water Radiation that can be 
Supplied on a Zero Day toy One Boiler Horse-Po-^ver ^vlien the 
Boiler is Used as a Heater: — Assuming that the coal used in 
the plant has a heating value of 13000 B. t. u. per pound, 



DISTRICT HEATING 321 

and that the efficiency of the boiler is 60 per cent., each 
pound of coal will transmit to the water 7800 B. t. u. Sincv. 
each pound of water takes up 25 B. t. u. on its passage 
through the heating boiler, one pound of coal will heat 312 
pounds, or 37.5 gallons of water. This is equivalent to sup- 
plying heat, under extreme conditions of heat loss, to 37.5 
square feet of radiation for one hour. One boiler horse- 
power, according to Art. 187, is equivalent to the expendi- 
ture of 970.4 X 34.5 = 33478 B. t. u. Now since each pound 
of coal transfers to the water 7800 B. t. u., one boiler horse- 
power will require 33478 -^ 7800 = 4.29 pounds of coal. If, 
then, the burning of one pound of coal will supply 37.5 
square feet of hot water radiation for one hour, one boiler 
horse-power will supply 4.29 X 37.5 = 160 square feet for 
one hour, and a 100 H. P. boiler will supply 16000 square feet 
of water radiation in the district for the same time. These 
figures have reference to boilers under good working condi- 
tions and probably give average results. 

1S9. Square Feet of Hot Water Radiation in the District 
that can be Supplied on a Zero Day by an Economizer Lo- 
cated in the Stack Gases between the Boilers and the Chim- 
ney; — In order to make this estimate it is necessary first to 
know the horse-power of the boilers, the amount of coal 
burned per hour, the pounds of gases passing through the 
furnace per hour and the heat given off fisom these gases 
to the circulating water through the tubes. 

Application. — Let C = pounds of coal burned per hour = 
boiler horse-power X pounds of coal per boiler horse-power 
hour, Wa = pounds of air passed through the furnace per 
pound of fuel burned, s = specific heat of the gases, U = 
temperature of gases leaving boiler, ts = temperature of 
gases leaving economizer, tw = temperature of water enter- 
ing- economizer and tf r= temperature of water leaving the 
economizer. Then, if 8.33 pounds of water will supply one 
square foot of radiation for one hour we have 

s X (C XWa + C) X iU — ts) 

Rw = ■ (121) 

8.33 X (tf — tw) 

In the illustrative plant, 44500 poiinds of steam per hour 

are generated in the steam boiler plant at a pressure of 125 

pounds gage. To find the boiler horse-power let the total 

heat of the steam, above 32° at 125 pounds gage, be 1192 

B. t. u., and let the temperature of the incoming feed water 



322 HEATING AND VENTILATION 

to the boilers be 60 degrees. (In most cases the feed water 
will be at a higher temperature, but since it will occasionally 
be as low as 60 degrees, this value should be used.) The 
heat put into a pound of steam under these conditions is 
1192 — (60 — 32) = 1164 B. t. u., and in 44500 pounds it will 
be 51798000 B. t. u. Since one horse-power of boiler service 
is equivalent to 33455 B. t. u., we will need 51798000 -^ 
33478 = 1548 boiler horse-power. This horse-power will 
take care of all the engines and pumps in the plant. If the 
coal used contains 13000 B. t. u. per pound and the boilers 
have 60 per cent, efficiency, 7800 B. t. u. will be given to the 
water per pound of fuel burned, and the amount of coal 
burned per hour will be 51798000 4- 7800 = 6640 pounds. 
This g-ives 6640 -^ 1548 = 4.3 pounds of fuel per boiler horse- 
power hour, and 6.7 pounds of water evaporated per pound 
of fuel. If the flue gases have 12 per cent. CO2, there are 
used according to experimental data, about 21 pounds of air 
or 22 pounds of the gases of combustion, per pound of fuel 
burned. This is equivalent to 6640 x 22 = 146080 pounds of 
flue gases total. Suppose now that these gases leave the 
furnace for the chimney at a temperature of 550 degrees F., 
that the economizer drops the temperature of the g-ases 
down to 350 degrees (a condition which is very reasonable) 
and that the specific heat of the gases is about .22, we have 
146080 X .22 X (550 — 350) = 6427520 B. t. u. given oft from 
the gases per hour in passing through the economizer (see 
numerator in Equation 121). This heat is taken up by the 
circulating water in passing through the economizer toward 
the outgoing main. Now if the water as it returns from the 
circulating- system, enters the economizer at 155 degrees, 
and leaves at 180 degrees, we will have 6427520 -f- (180 — 
155) = 257100 pounds of water heated per hour. This is 
equivalent to supplying 257100 -^ 8.33 = 30864 square feet of 
radiation per hour when the plant is running at its peak 
load. Taking the "pounds of steam per hour" in the above 
as the only variable quantfty, we are fairly safe in saying 
that the heat in the chimney gases from one horse-power of 
steaming boiler service will supply, through an economizer, 
30864 -=- 1548 =: 20 square feet of radiation in the district. 
In plants where only 7 pounds of water are allowed to each 
square foot of radiation per hour, this becomes 23.8 square 
feet of radiation instead. 



DISTRICT HEATING 323 

190. Square Feet of Gcononiizer Surface Required to 
Heat the Circulatingr Water in Art. 189: — Let K = the coeffi- 
cient of heat transmission through clean cast iron tubes and 
E = the efficiency of the tube surface when in average serv- 
ice, also let the terms for the temperatures of the gases and 
the circulating water be as given in Art. 189, then 

Heat trans, per hour from gases to water 
Re = (122) 



K X E X 



/ tb + ts tf 



2 / 

This equation assumes that the rate of heat flow through 

the tubes is the same at all points. As a matter of fact this 

rate changes slightly as the water becom.es heated, but the 

error is not serious in an equation, w^here the efficiency of 

the surface may be anything from 100 per cent, in new tubes 

to as low as 30 to 40 per cent, for old ones. 

■ Application. — Let K = 1 and E = A, then 

6427520 
Re = = 8125 sq. ft. 

(550 + 350 180 + 155 \ 
2 ^) - 

With 12 square feet of surface per tube this gives 677 tubes. 

191. Square Feet of Economizer Surface to Install when 
the Fcononiizer is to be Used to Heat the Feed Water for 
the Steaming Boilers: — If 30 pounds of feed water are f€d 
to the boiler per horse-power hour, and it K =: 7, E =: .4, 
/& = 550, ts = 350, tf = 250, and tw = 90 (about the lowest 
temperature at which water should enter the economizer), 
then the square feet of surface per horse-power is 

30 X (250 — 90) 
Re — — =: 6.1 sq. ft. 

(550 + 350 250 + 90 \ 
-1 -. ) 

192. Total Capacity of the Boiler Plant and the Number 
of Boilers Installed: — The following discussion on the size 
of the boiler plant is purely for illustrative purposes and 
is intended to show how such problems may be analyzed. 
In most cases the exhaust steam, and the economizer, if used, 
will fall far short of supplying the total radiation in the 
district, especially when the electrical output is light and 
the weather is cold. Suppose it be desired to install extra 
boilers to be used as heaters for the radiation not supplied 



324 HEATING AND VENTILATION 

from these two sources. To determine the amount of extra 
boilers, find the amount of radiation to be supplied by the 
exhaust steam and the economizer and subtract this from 
the total radiation. The difference must be supplied by boil- 
ers used as heaters. It is probably not safe to estimate too 
closely on the amount of exhaust steam given to the heating- 
system. The maximum amount of 44500 pounds per hour 
was obtained, in this case, by pumping one gallon of water 
per hour for each square foot of radiation and by pumping 
city water, in addition to that obtained from the engines. 
In heating, a less amount of water than this may be circu- 
lated even on the coldest day. This is possible, first, be- 
cause water may be carried at a higher temperature than 
that stated, and secand, because there may be less loss of 
heat in the conduit, thus giving more heat per gallon of 
water to the radiation. Again, in estimating for a city 
w^ater supply, the demands are not. very constant and are 
difficult to estimate. In this one design it was thought that 
44500 pounds per hour was a very liberal allowance and 
could be dropped to 35000 pounds (140000 square feet of radi- 
ation), when estimating the amount of radiation supplied 
by the exhaust steam. 

By Fig. 164 it will be seen that the minimum load on the 
steaming boilers carries through six hours out of the entire 
twenty-four and that the exhaust steam at this time drops 
to 22890 pounds per hour, supplying 91560 square feet of 
radiation. This minimum load is 51 per cent, of the max- 
imum, and 66 per cent, of the amount taken as an average, 
i. e., 35000. The work done by the economizer is fairly con- 
stant, since the amount of economizer surface lost by the 
steaming boilers under minimum load would be made up 
by the additional heating boilers thrown into service. On 
the hasis of 35000 pounds per hour, the exhaust steam and the 
stack gases together would heat 170960 square feet and 
there would be left 13540 square feet (184500 — 20 X 1548 — 
4 X 35000), to be heated by additional boilers. Under min- 
imum load this would be approximately 122500, leaving 62000 
square feet to be heated by additional boilers. If one boiler 
horse-power supplies 160 square feet of radiation, it would 
require 84 and 387 boiler horse-power respectively to supply 
the deficiency and the total horse-power needed in each case 
would be 1632 and 1935. A more satisfactory analysis, how- 



DISTRICT HEATING 325 

ever, is the following- which is worked on the hasis of 44^00 

pounds per h&iir. 

Let Ws = total number of pounds of steam used in the 

plant per hour = approximate number of pounds of exhaust 

steam available for heating- the circulating water per hour; 

We = equivalent number of pounds of steam evaporated from 

and at 212° ; \ = total heat, above 32°, in one pound of dry 

steam at the boiler pressure; q' = total heat, above 32°, in 

one pound of feed water entering the boiler; then, if the 

latent heat of steam at atmospheric pressure = 970.4 B. t. u. 

we have 

Ws (X — «') 

We = • (123) 

970.4 

and the corresponding boiler horse-power needed as steam- 
ing boilers will be 

We 

Bs. H. P. = • (124) 

34.5 

Next the radiation in the district that can be supplied 
by the exhaust steam is Rw = 4 Ws, and the amount sup- 
plied by the economizer is Re = 20 X B. H. P. From which 
we may obtain the capacity of the heating boilers, as 

Total Radiation — 4 Ws — 20 B. H. P. 

Bw. H. P. = (125) 

160 

The total boiler horse-power of the plant is, therefore, the 
sum of Bs. H. P. and Bw. H. P. To obtain Equation 125 for any 
specific case one must consider the maximum and minimum 
conditions of the steaming- boiler plant. Let Ws (max) = 
maximum exhaust steam, and Ws (min) = minimum exhaust 
steam. Then for the two following conditions we have, 
Case 1, where the steaming and heating boilers are independent of 
each other, the total boiler horse-power installed = Bs. E. P. + 
[total radiation — 4 Tf « (min) — 20 X B. H. P. in use] -^ 160. 
Also, Case 2, where a part or all of the steaming boilers are piped 
for both steaming and water service, the total boiler horse- 
power installed = Bs. H. P. + [total radiation — 4 Ws (max) — 
20 X B. H. P. in use] -^ 160. It will be noticed that the last 
term representing the economizer service is simply stated 
as boiler horse-power and no distinction is made between 
steaming or heating service. This term is difficult to esti- 
mate to an exact figure because it should be the total horse- 
power in use at any one time, both steaming and heating. 



326 HEATING AND VENTILATION 

and this can only be obtained by approximation. It makes 
no difference what service the boiler may be used for, the 
work of the economizer is practically the same. Probably 
the most satisfactory way is to substitute the value of 
Bs. H. P. for B. H. P. in the economizer and get the approx- 
imate total horse-power, then if this approximate total 
horse-power differs very much from that actually needed, 
other trials may be made and new values for the total horse- 
power obtained until the equation is satisfied. 

Application. — Let Ws = pounds of exhaust steam, X = 
1192 (125 pounds gage pressure), and q' = 28 (feed water 
at 60°); then when Ws — 44500 

We = 53400 

Bs. B. P. = 1548 

184500 — 4 X 22890 — 20 X 1548 

Bw. H. P. Case 1 = = 387 

160 

184500 — 4 X 44500 — 20 X 1548 

Bto. H. P. Case 2 = = —153 

160 

This shows that there is in excess of waste heat in Case 2, 
making- a total boiler horse-power, Case 1, =. 1935 and Case 
2, r= 1548. Investigating Case 1 to see what error was intro- 
duced by using 1548 in the economizer, we find approximately 
800 horse-power of steam boilers in use, and the total horse- 
power to be 1187, which is about 360 horse-power on the 
unsafe side. Substitute again and check results. Case 2 is 
reasonably close. In any case the most economical size of 
boiler plant to install in a plant requiring both steaming and 
heating boilers is one where at least a part, if not all, of the 
boilers are piped so as to be easily changed from one system 
to the other. By such an arrangement the capacity may be 
made the smallest possible. After obtaining the theoretical 
size of the plant, it would be well to allow a small margin 
in excess so that one or two boilers may be thrown out of 
commission for repairs and cleaning without interfering 
with the working of the plant. Case 2 seems to be the better 
arrangement. Assuming 1800 total boiler horse-pow^er we 
might very well put in six 300 H. P. boilers arranged in three 
batteries. 

193. Cost of Heating from a Central Station (Direct 
Firing): — It will be of interest in this connection to estimate 
approximately the fuel cost in supplying heat by direct firing 



DISTRICT HEATING 



32^ 



to one square foot of hot water radiation per year from the 
average central station. In doing- this make the boiler as- 
sumptions the same as Art. i88. Take coal at 13000 B. t. u. 





S£ 







ECONOMIXER 



POWER PLANT LAYOUT. 

Fig. 169. 

per pound, 2000 pounds per ton, and a boiler efficiency of 60 

per cent. Water enters the boiler at 155 degrees from the 



328 HEATING AND VENTILATION 

returns, and is delivered to the mains at 180 degrees. From 
the value of the coal we have 15600000 B. t. u. per ton given 
off to the water. This is equivalent to heating- 624000 
pounds, or 74910 gallons, of water. If one ton of coal costs 
3.50 at the plant, we have 

350 ^ 74910 = .0047 cent 
This represents the expense for fuel to reheat one gallon of 
water, or to supply one square foot of heating surface one 
hour at an outside temperature of zero degrees. Let the 
average outside temperature for the eight heating months 
be 39° (see Art. 63). This gives an average difference be- 
tween the inside and outside temperatures in, any residence 
of 70 — 39 = 31 degrees, and the equation for the heat loss. 
Art. 39, reduces to 31 -^ 70 = .44 of its former value. Now, 
if^ it takes one gallon of water per square foot of radiation 
per hour under maximum conditions, we have for the eight 
months .44 X 8 X 30 X 24 = 2535 gallons of water heated 
for each square foot of radiation, at a fuel expense of 2535 X 
.0047 =r 11.9 cents per square foot of radiation for the heat- 
ing year. 

When the plant is working under the best conditions 
this figure can be reduced. It can be done with boilers of 
a higher efficiency than that stated, or by using a cheaper 
coal, both of which are possible in many cases. 

194. Cost of Heating from a Central Station. Summary 
of Tests: — The following tests were conducted upon the 
Merchants Heating and Lighting Plant, LaFayette, Ind. ; one 
in 1906 and the other in 1908. The plant was changed slight- 
ly between the two tests and the radiation carried upon the 
lines was much increased, although in all essential features 
the plant was the same. The circulating water was heated 
by exhaust steam heaters and by heating boilers. 

The plant had the following important pieces of appara- 
tus employed in generating or absorbing the heat supply: 

BOILERS (Steaming and Heating). 

Two 125 H. P. Stirling boilers. Total heating surface 
2524 sq. ft. 

Three 250 H. P. Stirling boilers. Total heating surface 
7572 sq. ft. 

Pressure on steam boilers (gage), 150 lbs. 

Pressure on heating boilers (approx.), 60 lbs. 



DISTRICT HEATING 329 

ENGINES 

One 450 H. P. Hamilton Corliss comp. engine, direct con- 
nected to a 300 K. W. Western Electric 72-pole alternating 
current generator 120 R. P. M. This engine carried the load 
of the plant when it was above 50 K. W., which was generally 
from 5:30 A. M. to 11:30 P. M. When this unit was run, 
direct current was obtained by passing the alternating cur- 
rent through a motor generator set. 

One 125 H. P. Westinghouse comp. engine, belted to one 
75 K. W. 3-phase alternating and two direct current genera- 
tors, and run at 312 R. P. M. This ,unit was generally run 
between 11:30 P. M. and 5:30 A. M. 

One 250 H. P. Westinghouse comp. engine, belt connected 
to a 200 K. W. generator and two smaller machines. 

PUMPS. 

One centrifugal, two-stage pump, Dayton Hydraulic Co., 
direct connected to a Bates vertical high speed engine at 300 
R. P. M. 

Two Smith-Vaile horizontal recip. duplex pumps 14 in. X 
12 in. X 18 in. Each of the three pumps connected to the 
return main in such a way as to be able to use any combina- 
tion at any one time to circulate the water. The centrifugal 
pump had been in service only one season. It had a capacity 
about equal to the two reciprocating pumps and under the 
heaviest service this pump and one of the duplex pumps 
were run in parallel. 

One Smith-Vaile horizontal reciprocating tank pump 
6 in. X 4 in. X 6 in. to lift the water of condensation from 
the exhaust heater to the tank. 

One Smith-Vaile horizontal reciprocating make-up pump 
6 in. X 4 in. X 6 in. to replace the water that was lost from 
the system. 

Two National horizontal reciprocating boiler feed pumps. 

One 9% in. Westinghouse air pump, to keep up the sup- 
ply of air through the conduits to the regulator system in 
the heated buildings. 

One Deane vertical deep well pump, to deliver fresh 
water to the supply tank. 

One Baragwanath exhaust steam heater or condenser, 
having 1000 sq. ft. of heating surface. 



330 



HEATING AND VENTILATION 



PARTIAL SUMMARY OF RESULTS. 

1906 1908 

1. Square feet of radiation 118000 150000 

2. Temperature of circulating- water in 

deg-rees F., flow main 158.36 164.4 

3. Temperature of circulating water in 

degrees F., return main 139.9 139.6 

4. Temperature of circulating water in 

degrees F., after leaving heater 145.6 147. 

5. Temperature of outside air in de- 
grees F 32.6 37.5 

6. Temperature of stack gases in de- 
grees F., steaming boiler 566.8 

7. Temperature of stack gases in de- 
grees F., heating boiler 562. 656. 

8. Draft in stacks (all boilers average) 

in inches of water .689 .595 

9. Heating value of coal in B. t. u. 

per pound 12800 11565 

10. B. t. u. delivered to steaming boiler 

per hour by coal 18187000 25833000 

11. B. t. u. delivered to heating boilers 

per hour by coal 19226000 27917000 

12. B. t. u. delivered to circulating water 

by heating boilers per hour 11800000 15405000 

13. B. t. u. to be charged to heating boil- 
ers (Item 12— Item 15) 7650000 6934000 

14. B. t. u. delivered to circulating water 
by exhaust steam from the gener- 
ating engines per hour 3600000 6602000 

15. B. t. u. thrown away during test 
from pump exhausts and available 

for heating circulating water 4150000 8471000 

16. B. t. u. available for heating circu- 
lating water from all exhaust steam 
as in normal running (Item 14 -f- 

Item 15) .". 7750000 15073000 

17. Total B. t. u. given to circulating 

water per hour (Item 13 -|- Item 16). .15400000 22007000 

18. Gallons of water pumped per hour 

[Item 17 ~ (8.33 X Items 2—3)] 100000. 108000 



DISTRICT HKATINa 331 

19. Gallons of water pumped per square 
foot of radiation per hour (Item 

18 ~ Item 1) 85 .70 

20. Efficiency of heating boilers (Item 

12 -^ Item 11) approx 60 .55 

21. Value of the coal in cents per ton of 

2000 pounds at the plant 200. 175. 

22. Average electrical horse-power 68 141 

Note. — The above values are averages and were taken 
for each entire test. The B. t. u. values were considered 
satisfactory when approximated to the nearest thousand. 

195. ReMTulation : — The regulation of the heat within the 
residences is best controlled from the power plant. In most 
heating plants a schedule is posted at the power house which 
tells the engineer the necessary temperature of the circu- 
lating water to keep the interior of the residences at 70 
degrees with any given outside temperature. The Merchants 
Heating and Lighting Company mentioned above use the 
following schedule: 

Atmosphere Water Atmosphere Water 

60 deg. 120 deg. 10 deg. 190 deg. 

50 " 140 " " 200 " 

40 " 150 " —10 " 210 " 

30 " 160 " — 20 " 220 " 

20 " 180 " 

In addition, read the article by Mr. G. E. Chapman, pub- 
lished in the Heating and Ventilating Magazine, August, 
1912, page 23, in which he describes the methods used in 
regulating the Oak Park, 111., plant. 

In some heating plants the regulation is by means of air 
carried from the compressor at the power house through a 
main running parallel with the water mains in the conduits, 
and branching to each building where it is used under a 
pressure of 15 pounds to operate thermostats, which in turn 
control the water inlets to the radiators. A closer regula- 
tion is obtained in the latter system than in the former, but 
it is needless to say that the thermostats require careful 
adjustments and frequent inspections, and repairs. 

Diaphragms or chokes having different sized orifices may 
be placed on the return main from each building to regulate 
the supply. Those buildings nearest to the power plant 



332 HEATING AND VENTILATION 

have the advantage of a greater differential pressure than 
those farther away, hence should have smaller diaphragms. 
By increasing the resistance in the return line from any 
building the water circulates more slowly and has time to 
give ofC more heat to the rooms. With a high temperature 
of the water and a careful adjustment of the diaphragms 
it is possible to have the amount of water circulated per 
square foot of radiation reduced much below one gallon per 
square foot per hour. 

STEAM SYSTEMS. 

196. Heating l>y steam from a central station, compared 
with hot water heating, is a very simple process. The power 
plant equipment is corhposed of a few inexpensive parts, the 
operation of which is very simple and easily explained. 
These parts have but few points that require rational de- 
sign. Because of the simplicity and the similarity to the 
preceding discussion on hot water systems, the work on 
steam systems will be very brief. All questions referring 
to the construction of the conduit, the supporting of the 
pipes, the provision for contraction and expansion, and the 
draining of the pipes and conduits, are comraon to both hot 
water and steam systems and are discussed in Arts. 160 and 
161. A large part of the work referring directly to district 
hot wafer heating applies with almost equal force to steam 
heating. This part of the work, therefore, will deal with 
such parts of the power plant equipment as differ from 
those of the hot water system. 

Centralized steam heating may be classified under two 
general heads, high pressure and low pressure, referring to 
the pressures carried in the transmission lines. Ordinarily 
steam is generated at high pressure at the boiler, 60 to 150 
pounds gage, and reduced for line service to pressures vary- 
ing from 5 to 30 pounds gage, with a still further reduction 
at the building to pressures varying from to 10 pounds 
gage for use in radiators and coils. Where exhaust steam is 
used in the main, the pressure is not permitted to go higher 
than 10 pounds gage, because of the back pressure on the 
engine or turbine. Where exhaust steam is not used, the 
pressures may be carried as high as desired, thus allowing 
for a greater pressure drop in the line and a corresponding 
reduction in pipe sizes. (See Central Station Heating in De- 



DISTRICT HKATING 



333 



troit. Power, May 7, 1918). In large plants the necessity 
for hig-h pressures and small pipes is apparent. Even in 
lines carrying exhaust steam, high pressure feeders or 
boosters are frequently run parallel to the heating main and 
at stated points connect to the heating main through pres- 
sure reducing valves. Tacuiwi returns may be applied to cen- 
tral station work the same as to isolated plants. (See Art. 
159 — Returning the water to the power plant. Also, Chap. 
IX). 

The principles involved in the power plant end of a 
steam heating system may be represented by Fig. 170. It 
will be seen that the exhaust steam from the engines or tur- 
bines has four possible outlets. Passing through the oil 
separator, which removes a large part of the entrained oil, 
part of the exhaust steam is turned into the heater for use in 
heating the boiler feed water. The rest of the steam passes 
on into the heating system. If there is more exhaust steam 
than is necessary to supply the heating system, the balance 
may go to the atmosphere through the back pressure valve. 
When the heating system is not in use, as would be the case 
in the four warm months of the year, the exhaust steam 
may be passed into the condenser. 



BYPASS AROUND HEATER 
BACKPRESSURE VALVE 



TOHEATER AND 
BACK PRESS VALVE 



TD CONDENSER 




E STEAM 
FROM BOILERS 



Fig. 170. 



It is very evident, from what has been said before, that 
it would not be economical to condense the steam in a con- 
denser as long as there is a possibility of using it in the 
heating system. The increased gain in efficiency, when con- 
densing the exhaust steain under vacuum, is very small com- 
pared to the gain when this same steam is used for heating 



334 HEATING AND VENTILATION 

purposes. It would be also very poor economy to use any 
live steam for heating when there is any exhaust steam 
wasted. "When the amount of exhaust steam is insufficient, 
live steam is admitted through a pressure reducing valve. 
197. Drop in Pressure and the Diameter of the Mains: — 
The flow of steam in a pipe follows the same general law as 
the flow of water. The loss of head may be represented 
by the well known equation, 

hf = • (126) 

gd 

where hf = loss of head in feet, = coefficient of friction, 

V = velocity in feet per second, I = length of pipe in feet, 

d = diameter of the pipe in feet and g = 32.2. Substitute, 

hf rr: 144 p -^ D, where j) = drop in pressure in pounds and 

D = density of the steam, and find 

2 dilv^ D 

p = (127) 

lUgd 

The coefficient of friction is found to vary with the velocity 
of the steam and with the diameter of the pipe. Prof. Unwin 
found that for velocities of 100 feet per second (good prac- 
tice for transmission lines), it could be expressed as follows, 
where c is a constant to be found by experiment, 

3 

= c ' 

which when substituted in Equation 127, gives 

Iv^ D c 

(128) 
12gd ~ - - 

Let W = pounds of steam passing per minute and di = diam- 
eter of pipe in inches, then 

1 / 3.6 \ TFMc 

(129) 



20.663 




The recommended value of the constant c for steam is .0027. 
Prom this equation we may obtain any one of the five terms, 
di, W, p, I or D, if the other four are known or assumed. In 
the greatest number of practical problems the item desired 
is the diameter, rfi, and conditions must give the pounds of 
steam to be conveyed per minute, the pressure drop allow- 
able for its transmission, the length of transmission pipe and 



DISTRICT HEATING 335 

the steam pressure (or density). In a comparatively few 
problems W or p may be required and the other four items 
g-iven. 

APPLICATIONS BY THE USE OF EQUATION 129. 

Application 1. — A steam power main is to be designed to 
deliver 8400 pounds of steam per hour, at 100 lbs. gage pres- 
sure, through a distance of 1000 feet of straight pipe. What 
will be the diameter if the allowable pressure drop for this 
1000 foot run is first, 1 lb.; second, Vs lb.; third, 10 lbs.? 

Solution. — 8400 pounds per hour =z 140 pounds per min- 
ute. At 100 lbs. gage pressure the density of the steam is 



258 and p = 


1 / 3.6 \ 140 X 140 X 1000 X .0027 


20.663 1 c?i 1 (Zi5 X .258 


Reducing p 


• 9938 35768 


(h^ (Zi6 


when p 


=: 1, (7i = 6.9" (area 37.40); 7" main required. 


P 


=: 1/2, (h = 7.8" (area 47.78); 8" main required. 


p 


= 10, (h = 4.5" (area 15.90); 41/2" main required. 



Application 2. — A 4-inch steam heating main 700 feet 
long is receiving steam at 15 lbs. gage pressure and deliver- 
ing it at a pressure 1% lower. What quantity of steam is 
being delivered? What quantity will be delivered if a drop 
of three pounds is allowed? 



Solution. — .15 = f .0484 



.1742 \ W" X 700 X .0027 



1024 X .072 



.0919 TF2 X 700 X .0027 I 1 1 ofi 

.15 = ; W ' 



1024 X .072 \ .1736 



V^ 



7.9 lbs. per 



min. Since with everything else constant the quantity of 
steam varies as the square root of the pressure drop, for 
three pounds drop 7.9 : \/.15 as Wi : V 3, whence W^ = 4.5 X 
7.9 = 35.6 lbs. per min. 

Application 3.— The equivalent length of a 4-inch high 
pressure steam main is to be 1600 feet and it will be ex- 
pected to deliver 9000 pounds of steam per hour when the 
pressure is 150 lbs. gage. What pressure drop will be ex- 
perienced when delivering this amount? 



336 HEATING AND VENTILATION 

Solution. — 9000 pounds per hour = 150 pounds per min- 
ute. At 150 lbs. gag-e pressure the steam density is .3635, 

.1742 \ 150 X 150 X 1600 X .0027 
then p = i .0484 



( 



1024 X .3635 
23.8 lbs. 

APPLICATIONS BY TABLE. 

To avoid the time and labor required in solving Equa- 
tion 129, tables have been compiled and curves plotted. None 
of these time saving efforts, however, have produced a work- 
ing scheme which is perfectly general, as all have at least 
two of the five variables constant. Thus, Table 39, Appendix, 
was compiled from Equation 129, upon the basis of a con- 
stant pressure drop, p z= 1 pound, and a constant pressure 
of 100 lbs. absolute in the pipe. When these two conditions ob- 
tain, values may he read directly from the tahle, hut when the pres- 
sure or the pressure drop differs from these, corrective calculations 
must he applied to the tabular values. 

As may be observed from the equation, the drop in pres- 
sure is proportional to the square of the pounds of steam 
flowing per minute (other items constant) and the amount 
delivered at any other pressure drop than that of the table, 
(1 pound) will be found by multiplying the reading from the 
table by the square root of the desired pressure drop in 
pounds. Also, since the tveight of steam moved at the same 
velocity under any other absolute pressure is approximately 
proportional to the absolute pressures (other items constant), 
the amount delivered at a^iy other pressure w^ill be found by 
multiplying the reading from the table by the square root 
of the ratio of the absolute pressures. The use of the table 
w^ill be made clear by the following checks of Applications 
1, 2 and 3 above. 

Check 1. Since the pressure in Application 1 is 100 lbs. 
gage and the table is calculated for 100 lbs. absolute, quan- 
tities of steam, before insertion into table, must be multi- 



1- .^ V. 100 

piled Dy ^ _ Hence the check of that part of Applica- 

^ 115 

tion 1 having one pound drop is as follows: 

140 X -i/ — 130 lbs. corrected steam. In column 

^ 115 



DISTRICT HEATING 337 

under 1000 feet, find by interpolation that 130 lbs. per min- 
ute corresponds to a diameter of 6.9; therefore a 7-inch main 
is required. Before being ready to refer the quantity of 
steam to the table for checking that part having .5 lb. pres- 
sure drop, it is necessary to apply corrections for both pres- 
sure and pressure drop, thus, 

140 X -x . X -\l ■ = 185 lbs. corrected steam. Un- 

^ 115 ^ .5 

der 1000 feet, find by interpolation, that 185 lbs. per minute 

corresponds to a diameter of 7.8 = 8-inch main. 

Similarly the 10 lb. drop is corrected by 



140 X -% / X \l = 41.3 lbs. corrected steam. Un- 

^ 115 ^ 10 

der 1000 feet, find by interpolation, that 41.3 lbs, per minute 

corresponds to a 4% -inch main. 

Check 2. In Table 39, under 700 feet, at 4-inch diameter, 
the capacity of the main is given as 36.7 lbs. for the conditions 
of 100 lbs. pressure absolute and 1-lb. drop in pressure. The 

corrective factor for pressures is evidently -* / Like- 

^ loo' 



.15 
wise the corrective factor for pressure drop is-*' J From 

^ 1 



these conditions the capacity is 36.7 X 

100 
7.8 lbs. per min. For the 3-lb. drop, the corrective calcula- 



^100 ^1 



I 30 / 3 



tions are 36.7 X ^ x \ — = 35.5 lbs per min. 

^100 ^1 

Check 3. In Table 39, under 1600 feet, at 4-inch diam- 
eter the capacity of the main is given as 24.4 lbs. for condi- 
tions of 100 lbs. pressure absolute and 1-lb. drop in pressure. 
The corrective factor for pressures increases this as follows: 



24.4 X •^1 . — 31.3 lbs. per minute, being the capacity 

^ 100 
of the main at the proMem pressure, but at the pressure drop of 
the taUe, 1-lb. Since capacities are proportional to the square 
root of the pressure drops, 

31.3 : 150 as vT": V/Twhence p .z= 23 pounds drop. 



338 HEATING AND VENTILATION 

It will be seen that the corrections, necessary because 
of the two items assumed constant, are always made to 
affect the quantity of steam involved, and upon analysis the fol- 
lowing general directions for finding- either a required TT, as in 
Application 2, or a tabular W, as in Application 1, will be 
found to hold. 

T-, . ^ „r _ / pressure of table /' 

Required 1^ X -% / X \l 

' pressure required ^ drop required 

Tabular W 

Actual Steam = Steam from Table X 



drop in table 



V given pressure / gi 



iven drop 



pressure basis of table ^ drop in table 

Steam to be taken in Table = Actual Steam X 

V pressure basis of table / drop in tabh 
'■ ^ \ — ; — -. — 
given pressure ^ given drop 



198. Dripping the Condensation from the Mainss: — The 

condensation of the steam which takes place in the con- 
duit mains, should be dripped to the sewer or the return 
at certain specified points, through some form of steam 
trap. These traps should be kept in first-class condition. 
They should be inspected every seven to ten days. No pipe 
should be drilled and tapped for this water drip. The only 
satisfactory way is to cut the pipe and insert a tee with the 
branch looking downward and leading to the trap. The 
sizes of the traps and the distances between them can only 
be determined when the pounds of condensation per running 
foot of pipe can be estimated. 

199. Adaptation to Private Plants: — District steam heat- 
ing systems may be adapted to private hot water plants by 
the use of a "transformer." This in principle is a hot water 
tube heater which takes the place of the hot water heater 
of the system. It may also be adapted to warm air systems 
by putting the steam through indirect coils and taking the 
air supply from over the coils. 

200. General Application of the Typical Design: — The 

following brief applications are meant to be suggestive of 



DISTRICT HEATING 339 

the method only, and the discussions of the various points 
are omitted. 

Square feet of radiation in the district. — 

Rs = 184500 X 170 ^ 255 = 123000 square feet. 

Amount of heat needed in the district to supply the radiation for 
one hour in zero weather. — ^, 

Total heat per hour = 123000 X 255 = 31365000 B. t. u. 

Amount of heat necessary at the potoer plant to supply the radia- 
tion for one hour in zero xoeaiher. — Assuming- 15 per cent, heat 
loss in the conduit (this is slightly less than that allowed for 
the hot water two-pipe system, 20 per cent.), we have 
31365000 -^ .85 = 36900000 B. t. u. per hour. 

Total exhaust steam available for heating purposes. — 
Ws (max.) = (23100 + 8680) X 1-15 = 36547 pounds per hour. 
Ws (min.) = ( 1490 + 8680) X 1-15 = 11696 pounds per hour. 

Total B. t. u. available from exhaust steam per hour for heating. — 
Let the average pressure in the line be 5 pounds gage and 
let the water of condensation leave the indirect coils in the 
residences at 140 degrees. We then have from one pound of 
exhaust steam, by Equation 97, 

B. t. u. r= .85 X 960 + 196 — (140 — 32) = 904 
Assuming this to be 900 B. t. u. per pound, the total available 
heat from the exhaust steam for use in the heating system is, 
maximum total = 32892300 B. t. u. and the minimum total, = 
10526400 B. t. u. 

Square feet of steam radiation that can be supplied by one pouyid 
of exhaust steam at 5 pounds gage. — 

Rs = 900 -f- (255 4- .85) = 3. 

Total B. t. u. to be supplied by live steam. — 
B. t. u. (max. load) = 36900000 — 32892300 = 4007700 B. t. u. 
B. t. u. (min. load) = 36900000 — 10526400 = 26373600 B. t. u. 

Total pounds of live steam necessary to suppleinent the exhaust 
steam. — Let the steam be generated in the boiler at 125 
pounds gage. With feed water at 60 degrees 

Ma.x. load = 4007700 -f- 1164 = 3444 pounds. 
Min. load = 26373600 ^ 1164 = 22661 pounds. 

Boiler horse-power tieeded fw the steam po%oer units. — As in 
Arts. 189 and 192, 

Bs. H. P. (max.) = 36547 X 1.2 -^ 34.5 = 1271. 
Bs. H. P. (min.) = 11696 X 1.2 -^ 34.5 = 407. 

Total boiler horse-power needed in the plant. — Maximum load. 
B. n. p. (total) = 1271 + (3444 X 1.2 ^ 34.5) = 1391. 



340 



HEATING AND VENTILATION 



It will be noticed that this total horse-power is 157 
horse-power less than the corresponding Case 2 in Art. 192. 
This is accounted for by the fact that no steam is used up in 
■work in the circulating pumps, also that the conditions of 
steam generation and circulation are slightly different. 1500 
boiler horse-power would probably be installed in this case. 

Size of conduit mains. — Let it be required to find the diam- 
eters of the main system in Fig. 166 at the important points 
shown. Art. 169 gives the length of the mains in each part. 
Allow .3 pound of steam for each square foot of steam radia- 
tion per hour (this will no doubt be sufEicient to supply the 
radiation and conduit losses). Try first, that part of the line 
between the power plant and A, with an average steam pres- 
sure in the lines of about 5 pounds gage and a drop in pres- 
sure of 1^/^ ounces per each 100 feet of run (approximately 
5 pounds per mile). 25200 pounds per hour gives W = 420. 
The length of this part of the line is 200 feet and the drop is 
3 ounces, or .19 pound. 

420 
W (table) = X -xl = 2158 pounds 



100 
20 



V.19 
which gives a 15 inch pipe. 

Following out the same reasoning for all parts of the 
line, we have 

TABLE XXXIX. 



pp 

to A 


AtoB 


B to 


OtoD 

■ 


200 


500 


150O 


1500 


84000 


57000 


34000 


l&OOO 


.19 


.47 


1.4 


1.4 


15 


13 


11 


9 



DtoE 



Distance between points 

Radiation supplied, sq. ft 

Pressure-drop in pounds — p 

Diam. of pipe in inches, by table. 



In general practice, these values would probably be 
taken 16, 14, 12, 10 and 6 inches respectively. Look up 
Table 39, Appendix, and check the above figures. 



CHAPTER XIV. 



TEMPERATURE CONTROL. IN HEATING SYSTEMS. 



201. From tests that have been conducted on heating- 
systems, it has been shown that there is less loss of heat 
from building's equipped Avith automatic temperature con- 
trol, than from buildings where there is no such control. A 
uniform temperature w^ithin the building is desirable from 
all points of view. Where heating systems are operated, 
even under the best conditions without such control, the 
efficiency of the system would be increased by its applica- 
tion. No definite statement can be made for the amount of 
heat saved, but it is safe to say that it is between 5 and 20 
per cent. A building- uniformly heated during the entire 
time, requires less heat than if a certain part or all of the 
building were occasionally allowed to cool off. When a 
building falls below normal temperature it requires an extra 
amount of heat to bring it up to normal, and when the in- 
side temperature rises above the normal, it is usually low- 
ered by opening windows and doors to enable the heat to 
leave rapidly. High inside- temperatures also cause a corre- 
spondingly increased radiation loss. Fluctuations of tem- 
perature, therefore, are not only undesirable for the occu- 
pants, but they are very expensive as well. 

202. Principles of the System: — Temperature control 
may be divided into two general classifications, — small plants 
and large plants. The control for small plants, i. e., such plants 
as contain very few heating units, is accomplished by regu- 
lating the drafts by special dampers at the combustion 
chamber. This method controls merely the process of com- 
bustion and has no especial connection with individual reg- 
isters or radiators, it being assumed that a rise or fall of 
temperature in one room is followed by a corresponding 
effect in all the other rooms. This method assumes that all 
the heating units are very accurately proportioned to the 
respective rooms. The dampers are operated by a motor 
device which in turn is driven by springs or weights and 
controlled by a thermostat and electric batteries. This 
system of regulation may be applied to any system of heat. 



342 



HEATING AND VENTILATION 



Thermosfaf set on wa// 
/n room abo\/e 




Fig-. 171 shows a typical appli- 
cation to a small steam boiler 
plant. Furnace systems require 
thermostatic control only be- 
tween the room and the dam- 
pers; closed hot water, steam 
and vapor systems, however, 
should have additional regula- 
tion from the pressure w^ithin 
the boiler to the draft. Occa- 
sionally in the morning the 
pressure in these systems may 
become excessive before the 
house is heated enough for the 
thermostat to act. With such 
dual regulation no hot water 
heater or steam boiler would be 
forced to a dangerous pressure. 
Fig. 172 represents a standard 
form of the thermostat supplied 
Fig. 171. by the Andrews Heating Co. 

and the Minneapolis Regulator Co. The complete regulator 
has in addition to this, two cells of open circuit battery and 
a motor box (Fig. 171), all of which illustrate 
very well the thermostatic damper control. 

The thermostat operates by a differential 
expansion of the two different metals com- 
posing the spring at the top. Any change in 
temperature causes one of the metals to ex- 
pand or contract more rapidly than the other 
and gives a vibrating movement to the project- 
ing arm. This is connected with the batteries 
and with the motor in such a way that when 
the pointer closes the contact with either one 
of the contact posts, a pair of magnets in the 
motor causes a crank arm to rotate through 
180 degrees. A flexible connection between this 
crank and the damper causes the damper to 
open or close. A change in temperature in 
the opposite direction makes contact with the 
other post and reverses the movement of the 




TEMPERATURE CONTROL 



343 




Fig. 173. 



crank and clamper. The 
movement of the arm be- 
tween the contacts is very 
small thus making- the 
thermostat very sensitive. 
No work is required of the 
battery except that neces- 
sary to release the motor. 

Occasionally it is desira- 
ble to connect small heat- 
ing plants having only one 
thermostat in control, to a 
central station system. Fig. 
173 shows how the supply 
of heat may be controlled 
by the above method. 

Temperature control in large 
plants, i. e., those plants 
having a large number of 
heating units, is much more 
complicated. The following 
discussion will apply espe- 
cially to hot water and 
steam systems, and will be 
additional to the control at 




Fig. 174. 



344 



HEATING AND VENTILATION 




Fig. 175. 



the heater and boiler as discussed under small plants. Fig. 
174 shows a typical layout of such a system. Compressed 
air at 15 pounds gage is maintained in cylinder", Su, which is 
located in some convenient place for the attendant. This air 
is carried to the thermostat, Th, on one 
of the protected walls in the room. Here 
it passes through a controlling valve 
and is then led to the regulating valve 
on the radiator where it acts on the top 
of a rubber diaphragm as shown in Pig. 
175 to close the valve and to cut off the 
supply. When the room cools off, the 
controlling valve at Th cuts off the sup- 
ply and opens the radiator air line to the 
atmosphere. This removes the air pres- 
sure from above the diaphragm and per- 
mits the stem of the valve to lift. On the 
opening of the valve the steam or water again enters the 
radiator and the cycle is completed. 

Fig. 139 shows the application of thermostatic control 
to blower work. In this system (single duct system) the 
thermostat B and the mixing dampers are located at the ple- 
num chamber. The same general arrangement may be ap- 
plied to the double duct system, with the dampers in the 
wall at the base of the vertical duct leading to the room. 

203. Some of the Important Points in tlie Installations — 

Each radiator has its own regulating valve. All rooms 
having three radiators or less are provided with one thermo- 
stat. Large rooms having four or more radiators have two 
or more thermostats with not more than three radiators to 
the thermostat. Where other motive power is not available 
for the air supply, a hydraulic compressor is used. This 
compressor automatically maintains the air pressure at 15 
pounds gage in the steel supply tank. The main air trunk 
lines are galvanized iron, %- and %-inch in diameter, and 
are tested under a pressure of 25 pounds gage. All branch 
pipes are %- and %-inch galvanized iron-. Fittings on the 
%-inch pipes are usually brass. Where flexible connections 
are made, this is sometimes done by armoured lead piping. 
Thermostats are usually provided with metallic covers and 
are finished to correspond with the hardware of the respec- 
tive rooms. Each thermostat is provided with a thermom- 



TEMPERATURE CONTROL 345 

eter and a scale for making- adjustments. Each radiator is 
provided with a union diaphragm valve having a specially 
prepared rubber diaphragm with felt protection. This valve 
replaces the ordinary radiator valve. One of these valves is 
used on the end of each hot water radiator, one on each one- 
pipe steam radiator and two on each two-pipe low pressilre 
steam radiators. This last condition does not hold for two- 
pipe steam radiators with mechanical vacuum returns, in 
which case patented specialties are applied by the vacuum 
company. In such cases the supply to the radiator only is 
controlled. In any first class system of control, the tempera- 
ture of the room may easily be kept within a maximum 
fluctuation of three degrees. 

204. Some Special Designs of Apparatus: — All tempera- 
ture control work is solicited by specialty companies, each 
having a patented system. In the essential features these 
systems all agree with the foregoing general statements. 
The chief difference is in the principle upon which the ther- 
mostat, Th, operates. 

Fig. 176 shows sections through the intermediate and 
positive thermostats manufactured by the Johnson Service 
Company, Milwaukee. The interior workings of the ther- 
mostats are as follows: Intermediate. — Air enters at A from 
the supply tank, passes into chamber B and escapes at port 
C. If thermostatic strip T expands inward to close C, the 
air pressure collects in B and presses down port valve Y, 
thus opening- port E, letting air through into F and out at O 
to close the damper. When T expands outward, pressure at 
B is relieved and Y is forced back by a spring, closing E. 
Air in F reacts against the diaphragm and escapes through 
hollow valve Y at U, permitting the damper to open. Posi- 
tive. — Air enters at A, passes into chamber B and escapes 
at C. If thermostatic strip T expands inward to close G, air 
pressure collects in B, forces out the knuckle joint K and 
operates the three-w^ay valve Y, thus shutting port E and 
opening port F, letting air escape and radiator valve open. 
When T expands outward, pressure at B is relieved, knuckle 
joint K returns, pulling Y outward, thus shutting port F, 
opening E, letting air escape through G and shutting off 
radiator valve. 

The real thermostat is the spring T. This is composed 
of steel and brass strips brazed together. Because of a 



346 



HEATING AND VENTILATION 



higher 'coefficient of expansion in the brass than in the 
steel, a change in the room temperature causes the spring 
to move toward or away from the seat C. T is adjusta.ble 
for any desired room temperature. The intermediate ther- 
mostat is used on indirect heating where mixing dampers 
are employed and where an intermediate position of the 
valve is necessary. The positive thermostat is used on direct 
radiators and coils where a full open or full closed move- 
ment of the valve is desired. 



INTERMEDIATE 



POSITIVE 



Fig'. 176. 



Fig. 177 shows a section through pattern K thermo- 
stat, manufactured by the Powers Regulator Co., Chicago. 
This thermostat consists of a frame carrying two corrugated 
disks, brazed together at the circumference and containing a 
volatile liquid having a boiling point at about 50 degrees F. 
At a temperature of about 70 deg^rees, the vapor within 
the disks has a pressure of about 6 pounds to the square 
inch. This pressure varies with every change of tempera- 



TEMPERATURE CONTROL 



347 



ture and produces variations in the total thickness of the 
center of the disks. 

The compressed air enters at H and passes into chamber 
y throug-h the controlling valve ./, which is normally held to 
its seat by a coil spring- under cap P. Within the flange M 
is located an escape valve L upon which the point of the 
supply valve / rests. Valve L tends to remain open when 
permitted by reason of the spring underneath the cap. When 
the temperature rises sufficiently to cause the disks to in- 
crease in thickness and move the flange M, the flrst action 
is to seat the escape valve L, its spring being weaker than 
that above /. If the expansive motion is continued after 





Fig. 177. 

valve L is seated, the valve / is then lifted from its seat 
and compressed air flows into the chamber 'N. As the 
air accumulates in chamber X, it exerts a pressure upon the 
elastic diaphragm K in opposition to the expansive force of 
the disk. So, whenever there is sufficient pressure in 2V to 
balance the power exerted by the disks, the valve J returns 
to its seat and no more air is permitted to pass through. 
If the temperature falls, the pressure within the disks be- 
comes less, the disks draw together and the over-balancing 



348 



HEATING AND VENTILATION 



air pressure in N reverses the movement of the flange M and 
permits the escape valve L under the influence of its spring 
to rise from its seat, whereupon a portion of the air in N 
is discharged until the pressure in N becomes equal to the 
diminished pressure from the disks. Thus the pressure of 
the air in N is maintained always in direct proportion to the 
expansive power (temperature) of the disks. Port / con- 
nects with chamber N and leads to the diaphragm valve. 

This thermostatic valve controls the regulator valve by 
a graduated movement and is used on the dampers for 
blower work. Another form with maximum movement only 
is designed for steam systems. 

Fig. 178 shows the positive and graduated thermostats 
as manufactured by the National Regulator company, Chi- 
cago. The thermostatic element in these thermostats is the 
vulcanized rubber tube A, which changes its length with the 
varying room temperatures and causes the valve O to open 
or close the port G, thus controlling the supply of air to 



POSITIVE 



INTERMEDIATE 





Fig. 178. 



and from the radiator valve or the regulating damper. In 
the positive thermostat air enters the tube from the supply 
through the filter and restricted passage P. From the in- 
terior of the tube the air leaves through the middle orifice 
and enters the pipe leading to the radiator valve. If the 



TEMPERATURE CONTROL 349 

room temperature is above the normal, port G closes and the 
air pressure collects in the tube, thus creating- a pressure 
in the line leading to the radiator valve and closing- it. If 
the room temperature falls below the normal, port G opens, 
air is exhausted from the tube to the atmosphere, the pres- 
sure on the radiator valve is released and the valve opens. 
The intermediate thermostat differs from the positive ther- 
mostat in having but one air line. Room temperatures 
below the normal contact tube A, open port G^, and exhaust 
the air to the atmosphere. With this release in pressure in 
the pipe at P the regulating- damper is turned to admit 
more warm air into the room. With the room temperature 
above the normal, tube A expands, port Q closes, pressure in 
pipe P increases and the regulating damper is turned so as 
to admit a lower temperature of air in the room. By means 
of this a graduated movement of the damper is obtained. 



CHAPTER XV. 



ELECTRICAL HEATING. 



In the present state of the heating business it seems 
almost unnecessary to discuss electrical heating, in any 
serious way, in connection Avith steam poAver plants. The 
reasons will he seen in the following brief discussion. 
Electrical heating" can appeal to the public only from the 
standpoint of convenience, since a comparison of economies 
between steam, hot water or warm air heating on one hand, 
and electrical heating on the other, is wholly against the 
latter. Its application to the process of heating will find 
its greatest economy in connection with water power plants 
where the combustion of fuel is eliminated from the prop- 
osition. This discussion will not bear in any way upon the 
water power generator. 

205. Equations Employed in Electrical Heating Design ;— 
1 H. P. = 746 watts. 

1 H. P. = 33000 ft. lbs. per min. = 1980000 ft. lbs. per hr. 

1 B. t. u. = 778 ft. lbs. 

1 H. P. hr. = 1980000 4- 778 = 2545 B. t. u. per hr. 

1 H. P. hr. zn 746 watt hours = 2545 B. t. u. per hr. 

1 watt hr. = 3.412 B. t. u. per hr. 

1 watt hr. = 3.412 -^ 170 = .02 sq. ft. of hot water rad. 

1 watt hr. = 3.412 -^ 255 = .0134 sq. ft. of steam rad. 

1 kilo-watt hr. = 20.1 sq. ft. of hot water rad. (130) 

1 kilo-watt hr. = 13.4 sq. ft. of steam rad. (131) 

206. Comparison between Electrical Heating and Hot 
Water and Steam Heating: — The loss in transmitting elec- 
tricity from the generators through the switchboard to the 
radiators may be small or large, depending upon the condi- 
tions of wiring, the current transmitted and the pressure on 
the line. In all probability it would equal or exceed the 
transmission losses in hot water or steam lines. Assuming 
these losses to be the same, a fair comparison may be made 
in the cost of heating by the various methods. The operat- 
ing efficiency of an electric heater is 100 per cent., since all 
the current that is passed into the heater is dissipated in 



ELECTRICAL HEATING 351 

the form of heat and no other losses are experienced. This 
is not true of steam systems where the water of condensa- 
tion is thrown away at fairly high temperatures. Where 
electricity or steam is g-enerated and distributed all in the 
same building-, there is no line loss to be accounted for, 
since all of this heat goes to heating the building and counts 
as additional radiation. 

Equations 130 and 131 show the theoretical relation 
existing between electrical heating and hot water and steam 
heating compared at the power plant. The following dis- 
cussion is based, therefore, upon the assumption that 1 kilo- 
watt hour, in an electric radiator, will give off the saine 
amount of heat as 20.1 and 13.4 square feet of hot water and 
steam radiation respectively. With coal having 13000 B. t. u. 
per pound and a furnace efficiency of 60 per cent., it will 
require 3412 -^ 7800 = .44 pound of coal per hour. If coal 
costs $2.00 per ton of 2000 pounds, there will be an actual 
fuel expense of .044 cent. On the other hand, assuming the 
combined mechanical efficiency of an engine or turbo-gener- 
ator set to be 90 per cent., the heat from the steam that is 
turned into electrical energy per hour is 1000 -^ .90 = 1111 
watts, for each kilo-watt delivered. Now if this unit has 
15 per cent, thermal efficiency, vv^e have the initial heat in 
the steam equivalent to 1111 -=- .15 = 7400 watt hours. From 
this obtain 7400 X 3.412 = 25249 B. t. u. per hour; or, 25249 -^ 
7800 = 3.2 pounds of coal per hour. This, at the same rate 
as shown above, would be worth .32 cent. Comparing, the 
electrical generation actually costs 7.2 times as much as the 
other. This comparison has dealt with the fuel costs at the 
plant and has not taken into account the depreciation, labor 
costs, etc., the object being to show relative efficiencies only. 

Another way of looking at this subject is as follows: a 
fairly large turbo-generator set (say 500 K. W.) will deliver 
1 kilo-watt hour to the switchboard on 20 pounds of steam. 
With 10 per cent, additional steam for auxiliary units, this 
amounts to 22 pounds of steam per kilo-watt hour at the 
switchboard. One pound of steam generated in a plant of 
this kind with the above efficiencies and value of coal, also 
with a steam pressure of 150 pounds and a good feed water 
heater, will give to each pound of steam approximately 1000 
B. t. u. This makes 22000 B. t. u. or 2.8 pounds of coal re- 



352 HEATING AND VENTILATION 

quired to each kilo-watt output. This is about 10 per cent, 
less than the above figures. 

The ratio of 7 to 1, as shown in the above efficiencies, 
does not seem to hold good in the selling price to the con- 
sumer. In round numbers, district steam and hot water 
heating systems supply 25000 B. t. u. to the consumer for 
one cent. The cost for electrical energy to the consumer is 
betw^een 6 and 7 cents per kilo-watt. This gives 3412 -=- 
6.5 = 525 B. t. u. for one cent. Comparing with the above, 
gives a ratio of 48 to 1. 

207. * The Probable Future of Electrical Heating: — Be- 
cause of the low efficiency of electrical heating as compared 
with other methods of heating, it is very probable that it will 
not replace the other methods in sections of the country 
having severe or changeable climate, except in so far as the 
convenience of the user is the principal thing sought for, and 
the expense of operating a minor consideration. 

On the other hand, in limited sections of the country 
where conditions are favorable (sections of the Pacific Coast 
for example), heating by electricity is rapidly increasing. 
Hydro-electric power at a low^ rate and a climate that re- 
quires only a small amount of heat in the buildings, morn- 
ing and evening, make electric heating an actual economy. 
In such a climate the cumbersome coal and oil burning steam 
and water heating systems would be inappropriate, while 
the starting and the banking of fires when not needed would 
be a wasteful process. 

While in most cases electricity will be barred from the 
usual heating and laundry processes, it will continue to be 
increasingly used in those household economies where tem- 
peratures are needed above 250°, such as percolators, grills, 
toasters, broilers, plate warmers, ranges and ovens. Electric 
ovens in bakeries are being einployed because they occupy 
much less space than the brick oven of same capacity, are 
light in weight, are inore cleanly, can be regulated more 
easily and use the heat generated much more effectively. 



CHAPTER XVI. 



REFRIGERATION. 



DESCRIPTION OP SYSTEMS AND APPARATUS. 

20S. General Divisions of the Subject: — The rapidly in- 
creasing- demand for the cold storage of food products, the 
production of artificial ice and the cooling of buildings have 
developed for the heating engineer a broad and inviting 
field, namely, refrigeration. A municipal electric or pump- 
ing station with a district heating plant to utilize the ex- 
haust steam in winter and a refrigeration plant to utilize 
the same in summer furnishes a unique opportunity for 
economic engineering. One application of the above princi- 
ple where a 10-ton ice plant of the absorption type was so 
operated in a town of 3500 population and earned a dividend 
of 13 per cent, on the investment, is proof, if any is needed, 
that the field is an intensely practical one. 

As in heating systems there must be sources of heat, 
circulating mediums, distributing systems and delivering 
systems whereby the carriers give up their heat at the 
proper places in the circuits, so in refrigerating systems 
there must be sources of minus heat or of heat abstraction, 
circulating mediums, distributing systems and receiving sys- 
tems whereby the carriers take up heat at the proper places 
in the circuits from articles or rooms that are being cooled. 
The carriers (circulating mediums), and the receiving and 
transmitting of the heat to and from them present no special 
difficulties or great diversity of practice, but in the methods 
of producing and maintaining the sources of minus heat 
there are considerable differences and numerous methods. 

209. Refrigerating Systems may be divided into two 
groups, those producing cold by more or less chemical action 
between ingredients upon mixing, called chemical systems, and 
those producing cold by the evaporation of a liquefied gas 
or the expansion of a compressed gas, called mechanical sys- 
tems. Chemical systems are used only occasionally in com- 
mercial work, but are frequently found in small sized plants 
for domestic purposes. Low first cost and convenience of 



354 



HEATING AND VENTILATNON 



handling' are the principal advantages. This division in- 
cludes the simple melting of ice and the mixing- of ice and 
salt for temperatures as low as to — 5 degrees. The latter 
is much used in domestic processes for the production of 
table ices. etc. Other ingredients .used in the mixtures with 
the corresponding temperature drops which may be ex- 
pected are given in Table 58, Appendix. The chemical 
method of producing cold is occasionally used to maintain 
low temperatures in storage rooms while repairs are being 
made upon the regular machinery. The chemical methods 
of cooling are so simple in principle that they will not be 
discussed further in this work. Mechanical systems include 
all the practical methods of commercial refrigeration. These 
are, the vacuum system, the cold air system, the compression system 
and the aljsorption system. 



210. Vacuum Systems: — This system was formerly of 
some importance but of late years has given place to other 
and more efficient methods. Fig. 179 shows a vacuum sys- 
tem in diagram. If a spray of water 
or brine is injected into a chamber 
that contains pans of sulphuric acid 
and is kept at a partial vacuurn of 
one or two ounces, the acid absorbs 
the water vapor from the spray, thus 
assisting in maintaining the vacuum 
and lowering the temperature of the 
remainder of the spray. The vapor- 
ization of the part that is absorbed 
by the acid requires heat. This 
heat is taken from the liquid of the 
spray that is not absorbed, conse- 
quently the temperature of the re- 
maining liquid is lowered. In a 
system of this kind a temperature 
of 32 degrees may easily be ob- 
tained. The water or brine after 
cooling- is then circulated through 
the coils of the cold storage room 
where it takes up the heat of the room and contents and 
returns to the vacuum chamber to be again partially evapo- 
rated and cooled. 



;ii 



A 



=^ 



Fig. 179. 



REFRIGERATION 



355 



211. Cold Air System: — The cold air system is used prin- 
cipally on ship board. Fig-. 180 shows diagrammatically the 
parts and the operation of the system. The cycle has four 
parts, compression in one of the cylinders of the compressor, 
cooling in the air cooler by g-iving- off heat to the cold water 




Fig:. 180. 



thus removing the heat of compression, expansion in the sec- 
ond cylinder of the compressor thus cooling the air, and 
refrigeration in the cold storag^e room where the heat lost dur- 
ing expansion is regained from the articles in cold-storage. 
Cold air machines work at low efficiencies because of the 
necessarily large cylinders and their attendant losses due 
to clearance, heating of the compression cylinder, snow in 
the expansion cylinder and friction. The system has much 
to recommend it, hoM^ever, since it is extremely simple, occu- 
pies a very small space compared with other systems and 
uses no costly gases, chemicals or supplies. 

212. The Compression and the Absorption Systems have 
in common this fact — both use a refrigerant, i. e., a liquid hav- 
ing a comparatively low boiling point. Perhaps the most 
common refrigerant is anhydrous ammonia, which boils at 
atmospheric pressure, at 28.5 degrees below zero and in 
doing- so absorbs as latent heat 573 B. t. u. Table 59, Ap- 
pendix, gives further properties. Other refrigerants used 



356 HEATING AND VENTILATION 

to a lesser extent are sulphur dioxide, SO2, which boils at 
— 14 degrees under atmospheric pressure with a latent heat 
of 162 B. t. u. and carbon dioxide, CO2, which boils at — 30 
degrees under a pressure of 182 pounds per square inch 
absolute with a latent heat of 140 B. t. u. A comparison of 
the temperatures and pressures of four common refriger- 
ants is given in Table 64, Appendix. Pictet's fluid is a mix- 
ture of 97 per cent, sulphur dioxide and 3 per cent, carbon 
dioxide. 

A choice of a universal refrigerant can scarcely be made 
because of the varying conditions of individual plants. The 
principal difficulty with the use of sulphur dioxide is the 
fact that any water uniting with it by leakage immediately 
produces sulphurous acid with its corroding action upon all 
the iron surfaces of the system. This same objection holds 
also for Pictet's fluid. The objections to the use of carbon 
dioxide are, first, its comparatively low latent heat, and 
second, the high pressure to which all parts of the apparatus 
and piping are subjected. Pressures of from 300 to 900 
pounds per square inch are very common. Perhaps the worst 
charge that can be made against ammonia as a refrigerant 
is that it is highly poisonous and corrodes metals, particu- 
larly copper and copper alloys. However, the high latent 
heat of ammonia, together with the fact that its pressure 
range is neither so high as with carbon dioxide, nor so low 
as with sulphur dioxide, are perhaps the chief reasons for 
the very general preference for ammonia as the commercial 
refrigerant in compression systems; while its great affinity 
for and solubility in water, are what make the absorption 
system a possibility. 

313. Compression System: — Compression machines may 
work well with the use of any one of the four refrigerants of 
Table 64, if the proper pressures and temperatures are ob- 
served and maintained. The common refrigerant for this 
type is, however, anhydrous ammonia, for reasons given 
above. Fig. 131 shows a diagrammatic sketch of the com- 
pression system. To follow the closed cycle of the ammonia, 
start with a charge being compressed in the cylinder of the 
compressor. Prom this it is conveyed by pipe to the con- 
denser which, being cooled by water, abstracts the latent 
heat of the refrigerant and condenses it to a liquid. From 
the condenser the liquid refrigerant is conveyed to the ex- 



REFRIGERATION 



357 



RErRIGERATOR 
ROOM AT 30 




COOLING WATER 



WARn BRINE 



LIQUID AnnONIA EXPANSION WLVE '-'°'J'° AnnONIA 

Fig. 181. 
pansion valve through which it expands into the evaporator 
or brine cooler. In changing from a liquid to a gas in the 
evaporator it absorbs from the brine an amount of heat 
equivalent to the heat of vaporization of the ammonia. 
Upon leaving the evaporator the refrigerant is again ready 
for the cylinder of the compressor, thus completing the 
cycle. 




TEN TON AMMONIA COMPRESSOR UNIVERSITY OF NEBRASKA 

Fig. 182. 
If the refrigerant is ammonia, the compressor is com- 
monly of the vertical type, direct connected to a horizontal 
Corliss engine as shown in Fig. 182. This type of com- 
pressor combines the high efficiency of the Corliss engine 
with the vertical type of compressor which is probably the 
best type for reliable service of valves and pistons. The 
vertical compressor is usually single acting with water 



358 



HEATING AND VENTILATION 




Fig. li 

jacketed cylinders. Horizontal compressors are usually- 
double acting", as shown in Fig. 183, where the prime mover 
is a direct connected electric motor. Poppet valves in this 
type are placed at an angle of 30 degrees to 45 degrees with 
the center line of the cylinder, a construction made neces- 




Fig. 184. 
sary by space restrictions on the cylinder heads. Compres- 
sors for other refrigerants are commonly of these same 
types, the main difference being that compressors for carbon 
dioxide systems are nearly always two-stage to produce 
high compressions. The intermediate cooler pressures range 



REFRIGERATION 



359 



from 300 to 600 pounds per square inch. Horizontal steam 
cylinders in tandem with the compressor cylinders are com- 
mon for the carbon dioxide systems and the compressor cyl- 
inders are usually single acting-. 

214. Condensers for Compression Systems are classi- 
fied under four heads, atmospheric condensers, concentric 
tube condensers, enclosed condensers and submerged conden- 
sers. An elevation of an atmospheric condenser is shown in 
Fig". 184. As illustrated it consists of vertical rows of pipes 
so connected by return bands as to make the hot refrig:erant 
pass throug-h each pipe beginning- at the top, while the cold 
water main at the top of the row furnishes a spray of"Water 
which trickles over the outside of the pipes. The gas on 
the inside of the pipes is thus cooled by the extraction of 
the quantity of heat that is used in raising the temperature 
of the water and evaporating a part of it. The complete con- 




LKHIO AMMONIA 

denser may consist of any required number of these vertical 
rows, placed side by side, each row properly connected to 
the hot gas header and to the liquid header. 

An elevation of one section of a concentric tube condenser is 
shown in Fig. 185. The arrows show the paths of the gas 
and water. As in the atmospheric type the gas enters at the 



300 



HEATING AND VENTILATION 



top and the liquid is drawn off below. In its descent it 
passes throug"h the annular space between the two concen- 
tric pipes and is cooled by the atmosphere on the outside of 
the larger pipes and by the water circulating through the 
inner pipes. This condenser has the advantage over the sim- 
ple atmospheric condenser in that the water may be made to 
have an upward course through the apparatus, thus bring- 
ing the coldest water in contact with the pipes carrying the 
liquid rather than with the pipes carrying the hot gas. 
Since the efficiency of the plant as a whole is very largely 
dependent upon the temperature of the liquid at the expan- 
sion valve this matter of the "counter flow" of the cooling 
water is an important one. For the medium sized and large 
compression systems this form of condenser is used almost 
without exception. 

The enclosed condenser (Fig. 186) is very similar to the sur- 
face coil condenser in steam engine 
plants. It consists of a cylindrical 
chamber with a number of concen- 
tric pipe spirals connecting a hot 
water header at the top with a cold 
water header at the bottom of the 
cylinder. The pipes of the spirals 
are provided with stuffing boxes 
where they pierce the upper and 
lower heads of the cylinder. With 
this condenser a counter flow of 
the water is used, the cold water en- 
tering the bottom of the coils and 
flowing upward, so that the liquid re- 
frigerant at the bottom of the cylin- 
der is very near the temperature of 
the incoming Avater. 

A sudmerged condenser, as the name 
implies, contemplates a rather large 
body of water below the surface of 
which there is submerged a coil for 
circulating the hot refrigerant. Fig. 
187 shows a section of such a con- 
jpj -|^gg denser. The hot gas enters at the 

top fitting of the coil and leaves at 
lower fitting. Cold water is constantly flowing in at the bot- 




REFRIGERATION 



361 



torn of the tank and leaving- by the overflow at the top, being 
heated as it rises. The form of the coil is usually spiral, 
although this condenser may be built with coils of the re- 

_ turn bend type when 

larger surface is re- 
quired. Only the small- 
er compression plants 
use the enclosed or the 
submerged type of con- 
denser. 

In general, con- 
densers may be consid- 
ered vital factors in 
the economy of com- 
pression plants. They 
must be reliable in 
service and economical 
in operation, and must 
be so designed and 
proportioned that they 
will deliver liquid re- 
frigerant within five 
degrees of the tem- 
perature of the incom- 
ing cooling water. A 
condenser should pre- 
sent all joints, particularly those holding the refrigerant, to 
plain view for easy inspection and repair. Since it is the func- 
tion of the condenser to dissipate the heat of the refrigerant 
gas, it is not uncommon to install it upon the roof or out- 
side the building in some cool place. This is especially true 
where the atmospheric or the concentric tube types are 
used. In such positions the heat radiated by the condenser 
is not given back to the rooms and piping systems. In addi- 
tion, the cooling action of the atmosphere assists in making 
the system more efficient. 




Fig. 137. 



215. Evaporators for compression systems may be con- 
sidered as condensers, reversed in action but very similar 
in form. If the refrigerating effect is accomplished by the 
brine cooling system an evaporator of some type will be 



362 



HEATING AND VENTILATION 



necessary, but if the refrig-eration is accomplished by circu- 
lating the expanding refrigerant itself, no evaporator is re- 
quired. Evaporators, or brine coolers, may be classifxed 
according to the method of construction, as shell coolers and 
concentric tube coolers. 

The shell cooler takes various forms. One is shown by 
Fig. 186, being in effect an enclosed condenser with brine 
instead of cold water circulating in the coils. The heat of 
the brine is transferred to the cool liquid refrigerant, caus- 
ing the refrigerant to evaporate and take from the brine 
an amount of heat equal to the latent heat of the refriger- 
ant. The proper height to which the liquid refrigerant 
should be allowed to rise in the evaporator is a very much 
disputed point, some old and experienced operators claim- 
ing greatest efficiency when about one-third of the cooling 

B 




Fig. 1 

surface is covered with liquid refrigerant leaving two- 
thirds to be covered with gaseous refrigerant. Others claim 
that the entire surface should be covered or "flooded" with 
liquid refrigerant. These points of view give rise to 
the two terms dry systems and flooded systems. Of late years 
the flooded systems are gaining somewhat in favor, a sepa- 
rator being installed between the evaporator and the com- 
pressor to prevent any liquid being drawn into the com- 
pressor cylinder. This separator drains any liquid which 
may collect therein, back into the evaporator. In the flooded 
system the brine cooler more commonly takes the form 
shown in Fig, 188, where at the end A D of the brine tank 
ABCD is shown the flooded cooler E. This cooler consists 



REFRIGERATION 363 

of a boilei' shell filled with tubes, the brine circulating- 
throug-h the inside of the tubes while the interior of the 
large shell is nearly or quite filled with liquid refrigerant. 

Concentric tuhe trine coolers are made of piping very similar 
in principle to that shown in Fig. 185, with the exception 
that instead of two concentric pipes, three are more com- 
monly employed. The brine circulates through the inner- 
most of the three and through the outermost, while the 
annular space between the smallest pipe and the middle 
pipe is traversed by the liquid refrigerant. In this way 
the annular space filled with refrigerant has brine on both 
sides and the cooling of the brine is very rapid. The numer- 
ous joints in this cooler present a constant source of trouble. 
Salt brine will usually freeze in the inner pipe, so that cal- 
cium chloride brine must be used. 

A choice of evaporators or coolers depends mainly upon 
whether the plant is to run continuously or intermittently. 
When run continuously only a small amount of brine is 
required, and this, when cooled quickly and circulated 
quickly, would call for a concentric tube cooler. "When run 
intermittently a much larger body of brine is desirable so 
as to remain cool longer during the night hours when the 
plant is not operating. For this condition a shell type 
cooler would probably be preferred. 

In addition to the condensers and evaporators that were 
described in detail, there are to be found on the well equip- 
ped compression system the following pieces of apparatus 
which will be mentioned and described only briefly. An oil 
separator is commonly found in the line connecting the con- 
denser with the compressor. This is simply a large cast 
iron cylinder with baffle plates to separate the oil from the 
ammonia. Since the oil is heavier than the ammonia it set- 
tles to the bottom and may be drawn off. An ammonia scale 
strainer is often found just before the compressor intake. 
Small purge valves are located at all high points in the 
system for the purpose of exhausting the foul gases or the 
air which may collect in the system. Such a purge con- 
nection is shown on the ;right end of the upper coil in 
Fig. 184. 

316. Pipes, Valves and Fittings for compressor refriger- 
ant piping are considerably different from the standard types. 
If the refrigerant is ammonia, no brass enters into the de- 



364 



HEATING AND VENTILATION 



sign of any part of the piping or auxiliaries traversed by the 
ammonia. The operating- principles of all valves are the 
same as standard ones but they are made heavier and en- 
tirely of iron, or iron and aluminum. The common threaded 
joint used on all standard fittings is replaced in ammonia 
systems by the bolted and packed joint. It is not w^ithin the 
scope of this w^ork to go into these details further than to 
give a section of an ammonia expan- 
sion valve (Pig. 189) and a section of a 
typical ammonia joint (Fig. 190). 





Fig. 189. Fig. 190. 

217. Absorption System: — As stated in Art. 190, the 
great affinity of ammonia gas for "water and its solubility 
therein, are what make the absorption system a possibility, 
and give it the name as well. At atmospheric pressure and 
50 degrees temperature one volume of water will absorb 
about 900 volumes of ammonia gas. At atmospheric pres- 
sure and 100 degrees temperature one volume of water 
will absorb only about one-half as much gas, or 450 vol- 
umes. If then, one volume of water is saturated at 50 de- 
grees with ammonia gas and heated to 100 degrees there 
will be liberated about 450 volumes of ammonia gas. Hence 
it is evident that a stream of water may be used as a con- 
veyor of ammonia gas from one place or condition to an- 
other, say from a condition of low temperature and pres- 
sure where the absorbing stream of water would be cool, to 
a condition of high temperature and pressure, where the 
gas would be liberated by simply heating the water. It will 
be noticed that the gas has been transferred as a liquid 
without a compressor or any compressive action, by pump- 



REFRIGERATION 



365 



ing a stream of water of approximately one-four hundred 
and fiftieth of the volume of the gas transferred. This, in 
the abstract, is the method employed in the absorption 
system to convey the ammonia gas from the relatively low 
tem.perature and pressure of the evaporator to the high 
temperature and pressure at the entrance of the condenser. 
The absorption system, when closely compared in prin- 
ciples of operation to the compression system, differs only 
in one respect, namely, the absorption system replaces the 
gas compressor by the strong and weak liquor cycle. As 



OR Of HER flff^ 



consisting 



shown in Fig. 191, both sys- 
tems have arrangements of 
condenser, expansion valve 
and evaporator that are iden- 
tical, hence the part of the 
cycle through these need not 
be considered. The problem 
of completing the cycle from 
evaporator t o condenser, 
however, is solved quite dif- 
ferently in the two systems. 
In the compression system 
(upper diagram) the evapo- 
rator delivers the expanded 
gas to the compres- 
sor, from which, 
under high pres- 
sure and tempera- 
ture, it is delivered 
to the condenser 
and the cycle is 
completed. In the 
absorption system 
(lower diagram) 
5° the evaporator de- 
livers the expanded 
gas to an absorber, 
in which the gas 
comes in contact 
with a spray of so- 
called weak liquor, 
water containing about 15 to 20 per cent. 




366 HEATING AND VENTILATION 

of anhydrous ammonia. The weak liquor absorbs the 
ammonia gas through which the liquor is sprayed and col- 
lects in the upper part of the absorber as strong liquor, contain- 
ing about twice as much anhydrous ammonia as the weak 
liquor, or 30 to 35 per cent. From here it is pumped through 
the exchanger (which will be ignored for the present) into 
the generator at a pressure of about 170 pounds per square 
inch gage. In the generator heat is supplied by steam coils 
immersed in the strong liquor. As this liquor is heated it 
gives up about half of the contained ammonia gas which 
rises and passes from the generator to the condenser, thus 
completing the ammonia or primary cycle, while the weak 
liquor flows from the bottom of the generator through the 
exchanger and pressure reducing valve back to the absorber, 
thus completing the secondary or liquor cycle. 

In general then, the absorption system uses two cycles, 
that of the ammonia and that of the liquor, the paths of the 
two cycles being coincident from the absorber to the gen- 
erator. The liquor pump serves to keep both cycles in mo- 
tion. The pump creates the pressure for both cycles and 
the expansion valve and the reducing valve reduce the 
pressure respectively for the ammonia cycle and the liquor 
cycle. The exchanger does not mix or alter the condition of 
the two streams of liquor passing through it, for its only 
function is to bring these two streams close enough that 
the heat of the weak liquor from the generator may be trans- 
ferred to the strong liquor going to the generator. Stated in 
other words, the exchanger heats the strong liquor by cool- 
ing the weak liquor, thus affecting a saving of heat which 
would otherwise be lost, since the weak liquor must be 
cooled before it is ready to properly absorb the gas in the 
absorber. 

318. An Elevation of an Absorption System with the 
elements piped according to what is considered best prac- 
tice is shown in Fig. 192. Starting at the expansion valve, 
the ammonia (liquid, gas or gas in solution) passes in order 
through these pieces of apparatus: the evaporator, the ab- 
sorber, the liquor pump, the chamber of the exchanger or the 
coil of the rectifier, the generator, the chamber of the recti- 
fier and the condenser back to the expansion valve. At the 
same time the liquor used to absorb the gas travels in order 
through these pieces: the absorber, the liquor pump, the 



REFRIGERATION 



367 



chamber of the exchanger or the coil of the rectifier, the 
generator, the pressure reducing- valve and the coil of the 
exchanger back to the absorber. The method of pipe connec- 
tion shown is a very common one although some varia- 
tion may be found, especially in the continued use of cool- 
ing water in consecutive pieces of apparatus. As shown, 
the cooling water is first used in the condenser. This will 
be found so in all plants. From the condenser the cooling 
water may next be taken to the absorber, as shown in the 
sketch, or it may be used in the rectifier coil instead of the 
strong liquor. In recent years the practice of by-passing 
a certain amount of the cool, strong liquor from the pump 
through the rectifier is gaining in favor. Fig. 192 shows 
a plant having bent coil construction. Plants are also built 
having a straight pipe construction, where all coil surfaces 
shown are replaced by straight pipes, the condenser being 
usually of the concentric tube atmospheric type and the 
evaporator being also of the concentric tube brine cooler 
type, as mentioned under compression systems. Both types 
of absorption plants are found in use. 



170 150 




DVALVC^ 



Fig. 192. 



368 



HEATING AND VENTILATION 



319. Generators are classified as horizontal and verti- 
cal. Fig-. 193 shows a horizontal type generator, with the 
analyzer and exchanger, and Fig. 194 shows the vertical 
type, also with the analyzer. The horizontal type may have 
one or more horizontal cylinders equipped with steam coils. 
The analyzer, which may be considered as an enlarged dome 
of the generator, is used to condense the water vapor which 
rises from the surface of the liquid in the generator. To 
do this the analyzer has a series of horizontal baffle plates 
through which the incoming cool, strong liquor trickles 




Fig. 193. 
downward while the heated mixture of ammonia gas and 
water vapor passes upward through interstices. In this 
way the strong liquor gradually cools the ascending water 
vapor and condenses much of it on the surfaces of the 
baffle plates. 

220. Rectifiers are arrangements of cooling surface 
designed to thoroughly dry the gas just before it passes 
into the condenser. This is accomplished by presenting to 
the hot product of the generator just enough cooling- sur- 
face to condense the water vapor without condensing any of 





Fig. 194. 



REFRIGERATION 369 

the ammonia gas. Rectifiers are 
very similar in general design to 

■^ the various types of condensers, 
there being atmospheric, concen- 
tric tube, enclosed and submerged 
rectifiers just as there are these 
same type of condensers, each de- 
scribed under the head of con- 
densers for compression systems. 
Rectifiers may save heat by the 
arrangement shown in Fig. 192, 
where the heat abstracted from the 
water vapor is given to the cool, 
strong liquor before entering the 
generator. As shown, the strong 
liquor may be divided, part pass- 
ing through the rectifier and part 
through the exchanger, or the 
strong liquor may all go through 
the exchanger first and then 
through the rectifier. Where 

strong liquor is so used, the recti- 
fier is always of the enclosed 
type. Rectifiers using water as 
the cooling medium are often 
called dehydrators, the term rec- 
tifier being more properly used 
when the cooling medium is the 
strong liquor. 

221. Condensers for absorption 
systems do not differ in design 
from those used for compression 
systems. The same types are used, 
and in the same manner, the sur- 
face being somewhat less due to 
the precooling effect of the recti- 
fiers or dehydrators. As a gen- 
eral statement, it is claimed that 
from 20 to 25 per cent, less surface 
is required in the condenser for an 
absorption machine than is re- 
quired in one for a compression 
machine. 




Fig.195. 



370 HEATING AND VENTILATION 

323, Absorbers may be classified as dry absorbers, wet 
absorbers, atmospheric absorbers, concentric tube absorb- 
ers and horizontal and vertical tubular absorbers. In the 
dry ahsorher, the top section of which is shown in Fig-. 195, 

the weak liquor enters at the 
middle of the top header and 
is sprayed upon a spray pan, 
from which it drips downward 
over the coils. The gas enters 
as shown, part being- delivered 
above the spray plate, so as to 
come into contact with the 
spray and the larger part being 
taken downward through the 
central pipe to a point near the 
bottom of the absorber, from 
which point it flows upward 
against the descending weak liquor by which it is absorbed. 
As the gas is dissolved by the weak liquor the heat of ab- 
sorption is given off, and taken up by the cooling w^ater in 
the coils. The result is a strong liquor which collects in 
the absorber ready to be delivered to the pump. 

The tvet absorber, on the contrary, has practically the 
whole body filled with weak liquor and th% ammonia gas 
enters near the bottom, bubbling up through the weak 
liquor thus saturating it. Various baffle plates with fine 
perforations break up the gas into small bubbles thus aid- 
ing in presenting a large surface of gas to the liquor 
which, as it becomes saturated and lighter, rises to the top 
of the body of the absorber and is ready to be drawn off by 
the pump. Instead of spiral cooling coils, this type is often 
made with straight cooling tubes inserted between two tube 
sheets, boiler fashion. This straight tube construction is 
much simpler and cheaper, and much more easily cleaned 
than the spiral type. It is favored by some on this account, 
especially where the cooling water has a tendency to form 
scale. 

Atmospheric absorbers resemble atmospheric condensers of 
the single tube type. The ammonia gas and weak liquor 
enter the bottom through a fitting commonly called a mixer, 
and the two flow upward through the inside of the pipe 
while the cooling water is in contact with the outside thus 
taking up the heat of absorption generated within the pipes. 



REFRIGERATION 371 

Coyicentric ttihe a'bsor'bers are very similar in design to con- 
centric tube condensers, the cooling' water passing through 
the central tube and the weak liquor and expanded gas en- 
tering at the bottom of the annular space and circulating to 
the top, absorption taking place on the way. Because of the 
small capacity of the last two mentioned absorbers, it is 
necessary to use with them an aqua ammonia receiver be- 
tween the absorber and the ammonia pump, to act as a 
reservoir for storing a reserve supply of the strong liquor. 

Horizontal and vertical tubular absorbers are those in which 
the cooling surface is composed of straight, horizontal or 
vertical tubes inserted between tube sheets, the cooling 
water flowing inside the tubes and the absorption taking 
place within the drum or bbdy of the absorber. 

223. Exchang-ers may be of two types, the shell type 
or the concentric tube type. The shell type, as the name im- 
plies, is composed of a main body or shell through which 
circulates the strong liquor to be heated and within this 
shell is a coil or other arrangement of heating pipes through 
which the hot, weak liquor flows. Fig. 192 shows the ele- 
mentary arrangement of such an exchanger. Concentric 
tube exchangers are used on large plants. They are similar 
in every way to the concentric tube condensers shown in 
Fig. 185, with the exception that larger pipes are needed 
for the exchangers. The cold, strong liquor is usually car- 
ried through the pipes and the hot, weak liquor through the 
annular space. The great advantage of this type of ex- 
changer is the same as that of the concentric tube con- 
denser, namely, the counter flow of the two streams. "With 
this arrangement the total transfer of heat is a maxiinum, 
for which reason this type of exchanger is generally pre- 
ferred. 

224. Coolers for the weak liquor are often found in 
plants. This piece of apparatus is not indicated in Fig. 192. 
It is usually installed as the lower three coils of the atmos- 
pheric condenser, and hence is simply a small condenser 
used to further cool the weak liquor just before its entrance 
into the absorber. With a counter flow, concentric tube ex- 
changer a weak liquor cooler is seldom found necessary. 

225. The Pump used in absorption systems to. raise the 
pressure of the strong aqua ammonia may be steam driven, 
electric driven or belt driven, as best suits the particular 



372 HEATING AND VENTILATION 

plant conditions. The power required by this piece of appa- 
ratus is about one horse power per 20 to 25 tons of refriger- 
ation capacity. 

226. Compression Systems and Absorption Systems Com- 
pared: — A comparison drawn between the compression sys- 
tem and the absorption system brings out the following 
facts: The compression system depends fundamentally upon 
the transferring of heat energy into mechanical energy and 
vice versa, with the attendant heavy losses. The absorption 
system merely transfers heat from one liquid to another. 
This is a process which is attended by only moderate losses. 
The compression system is comparatively simple, its pro- 
cesses readily understood and its machinery easily kept in 
good running order. The absorption system is complicated 
with a greater number of parts, its processes are often not 
thoroughly understood by those in charge and its m.achinery 
is likely to become inefficient because heat transferring sur- 
faces are allowed to become dirty. For these reasons the 
attendance necessary upon an absorption plant must be of a 
higher order than that necessary for a compression plant. 

227. Circulating Systems; — The refrigerating effect pro- 
duced by either one of the two systems may be delivered to 
the place of application in two ways. The first is the lyrine 
circulatiwi method w^herein a brine cooler is used through 
which the brine flows causing the evaporation of the liquid 
refrigerant and the cooling of the brine. This cold brine is 
then circulated through pipes to the place where refrigera- 
tion is desired. Pig. 188 shows an evaporator placed in one 
end of a large brine tank. The refrigerating effect is car- 
ried to the cans of w^ater by the circulation of this body of 
brine through the evaporator and out past the cans, the cir- 
culation through the channels shown being maintained by 
the pump. Brine, commonly used for such work, is made by 
dissolving calcium chloride in water. A 20 per cent, solu- 
tion is generally used. Salt brine is used to some extent 
but it has many disadvantages compared with calcium brine. 
The second method is the direct circulation metJiod wherein the 
liquid refrigerant is conveyed to the place to be cooled, is 
passed through an expansion valve and then circulated 
through coils in the space to be refrigerated, changing into 
gaseous form as fast as it can absorb enough heat. If 
ammonia is the refrigerant the direct circulation is not often 
favored because of its highly penetrative nature and odor. 



REFRIGERATION 



373 



even a leak so small as to escape detection being- sufficient 
to fill the refrigerated space with the odor, which many- 
food stuffs will absorb. 

338. There are Three Methods Employed, for Maintain- 
ing Liow Temperatures in storage and other rooms. The 
first is by direct radiation where the pipes are placed within 
the room and the refrigerant is circulated through them. 
This is the oldest, simplest and cheapest system to install. 
In this the proper location and arrangement of the pipes are 
essential to the most efficient operation. Since the tempera- 
ture to be maintained in a storage room depends upon the 
products to be kept in the room, it may be necessary to have 
a considerable range of temperature. It is desirable to have 
the pipes arranged as coils in two or three sets, each being 
valved so that the amount of refrigerant being circulated 
may be increased or decreased as the temperature of the 
stored product may require. 

The pipes should be set out from the wall several inches 
to give free air circulation and keep the frost that collects 
on them from coming in contact with the wall. The coils 
should be so placed that the temperature of all parts of the 
room may be kept as nearly uniform as possible. Some 
products keep as w-ell in still air as when it is in motion, but 
others, such as fruits, eggs, cheese, etc., are better pre- 
served when the air is circulated. Circulation may be ef- 
fected in a room piped for direct radiation by putting aprons 
over the coils as shown in Fig. 196. These aprons consist of 

12 inch boards D nailed to 
studding E and the whole 
fastened to the coils, the 
studding serving to keep the 
boards from coming into 
contact with the pipe coils. 
A false ceiling F is placed a 
few inches below the ceiling 
of the room so that the 
warm air flows toward the 
pipes and over them, drop- 
ping to the floor and passing 
out under the lower edge of 
the apron into the room, 
used drip pans should be 




Fig. 196. 
Wherever direct radiation is 



374 



HEATING AND VENTILATION 




placed directly underneath the coils in order to catch and 
drain off the water when the coils are cut out and the frost 
melts. This water should be drained into a receptacle that 
can be easily emptied when filled. 

The second method of room cooling is by indirect radiation. 
Let Pig". 197 represent a section of a storage building. The 
essential parts of the cooling system are, 
a bunker room AC, in the top part of the 
building, containing the cooling coils 
B, a series of ducts on either side of the 
building, so arranged that the air after 
passing over the cooling coils, drops 
downward. These ducts are provided 
with dampers for admitting as much of 
the cold air to the rooms as is desired. 
On becoming warmed this air is crowded 
out on the opposite side of the room into 
the ducts K and rises to the bunker- 
room where it is again cooled by passing 
over the coils. By the use of the damp- 
ers the cold air may be cut off from any 
room or admitted in large quantities 
thus making it an easy matter to main- 
tain the temperature at any point de- 
sired. The ducts leading the air from 
the rooms should be 25 per cent, larger 
than the ones leading to the rooms and 
the latter should have about three square 
inches cross-section per square foot of 
floor area in rooms having a ten foot 
ceiling. 

The third method is by means of a 
plenum system of air circulation, Fig. 198. The arrangements 
are quite similar to those of the plenum system for heating, 
except that the heating coils are replaced by the refrigerat- 
ing coils. The air required for ventilation is blown over the 
coil surface, erected in a coil or bunker room, over which, 
oftentimes, cold water is sprayed. This not only washes 
the air but tends to lower its temperature. If ammonia is 
used as a refrigerant, brine is circulated in the coils, but if 
carbon dioxide is used direct expansion is employed, thus 











fA 






hHBP ', 


^ / 


'^ 


Ak 


||||c \ 


iK 




W 




\\ 




G 


^t 




I 






u 


I 

\ 

A 






H/ 






r 




P 




E 


9 



Fig. 197. 



REFRIGERATION 



375 




T0^ 



Fig. 198. 



dispensing- with the use of 
brine. Tlie principal advan- 
tage of the plenum system of 
cooling- is that a positive cir- 
culation of air may be main- 
tained in any room even though 
the bunker room be placed on 
the first floor or in the base- 
ment of the building. This is 
the system used in large build- 
ings that are cooled during the 
summer as well as heated dur- 
ing winter, in factories where changes of temperature seri- 
ously affect the product, as in chocolate factories, in fur 
storage rooms, in drying the air before it is blown into blast 
furnaces and in the solution of many other important eco- 
nomic problems. 

239. Influence of the Dew Point: — In cooling a building 
by means of a plenum refrigerating system, great trouble 
is experienced with the formation of ice on the coils. For 
example, suppose such a cooling system on a hot summer 
day is taking in air at 90 degrees temperature and 85 per 
cent, humidity. If this air is cooled only ten degrees (see 
chart, page 29), it will have reached its dew point and as 
the cooling continues will deposit frost and ice on the coils 
from the liberated moisture, the air meantime remaining at 
the saturation point and being so delivered to the rooms. The 
undesirable feature of delivering saturated air to the rooms 
may be avoided by cooling- only part, say half of the air 
stream, considerably lower than the flnal temperature de- 
sired, and then mixing it with the other half, which is 
drier, before delivering it to the rooms. The troublesome 
coating- of ice and frost on the pipes may be avoided by 
combining the cooling- system with the air ^vashing system 
and using a brine spray instead of water for washing the 
air during cooling. The brine, which freezes at a very low 
temperature compared with water, plays over the cooling 
coils, and cleans both coils and air. The brine should pref- 
erably be a chloride brine. A modification of this method of 
avoiding- ice and frost is to provide pans above the coils 
and fill them with lumps of calcium chloride. The pans 
have perforations so arranged that as the strong chloride 



376 



HEATING AND VENTILATION 



solution forms (due to the deliquescence of the salt) it 
trickles down over the pipes and holds the freezing- point 
of any collecting- moisture far below the temperature of the 
coils. A sketch of this arrang-ement is shown in Pig-. 199, 
which has the disadvantag-e of the clumsy handling- of the 
calcium chloride. Plants operating- only during- the day, as for 




Fig. 1 



instance, auditoriums, commerce chambers, etc., often have 
no equipment for preventing- the accumulation of frost and 
ice, it being- allowed to form during- the short period of use 
and to melt during- the period of rest. 

330. Pipe Line Ref rigeration : — In a number of the 
larg-er cities refrig-eration is furnished to such places as 
cold storage rooms, restaurants, hotels, auditoriums, etc., 
by a conduit system or central station sj^stem. The leng-th 
of the mains in the various cities where used, rang-es from 
a few hundred feet to twenty miles and the circulating- 
medium employed is either liquid ammonia or brine. In the 
ammonia system two pipes are used, one carrying- the liquid 
ammonia to the place desired and the other returning- it 
after expansion to the central station. When brine is used 
it is g-ood practice to circulate it at from 12 to 15 degrees F. 
Occasionally the conduits carry three parallel pipes, two of 



REFRIGERATION 



which are foi^ circulating the brine and the third is for 
emergency cases. The line should be divided into sections, 
with valves and by-passes so arranged that a defective sec- 
tion could be repaired without interfering with the other 
parts. All valves should be readily accessible and all high 
points in the system should be equipped with purge valves. 
The service pipes should be two inches in diameter and well 
insulated. 

Either the ammonia absorption or compression system 
may be used for cooling the brine but according to Mr. Jos. 
H. Hart, the latter, making use of direct expansion, is the 
most efficient and the one most commonly installed. The 
loss by radiation to the pipes in the conduits is not great but 
numerous mechanical difficulties are yet to be overcome. It 
would seem desirable to make the pipe-line system of cool- 
ing general for residence use but as yet it has not been 

found economical to cool build- 
ings using less than the 
equivalent of 500 pounds of re- 
frigeration in 24 hours. Al- 
though not an efficient method, 
it seems probable that cold air 
refrigeration by using balanced 
expansion may supersede the 
other systems. 

231. As a Final Application 
of refrigeration we may men- 
tion the cooling of the drinking 
water supply in large office 
buildings, hotels, etc. Usually 
this is simply a small part of 
the work of a large refrigerat- 
ing plant. Fig. 200 gives a dia- 
grammatic elevation of such an 
arrangement. 




Fig. 200. 



CHAPTER XVII. 



REFRIGERATIOIV CALCULATIONS 



232. Unit Measurement of Refrigeration: — Since the 
first efforts toward refrig-eration employed the simple pro- 
cess of melting- ice by the abstraction of heat from nearby 
articles, it is not surprising- to find the accepted standard 
unit for expressing refrigeration capacities referred to the 
refrigerating effect of a known quantity of ice. In fact, 
since the latent heat of fusion of ice is a constant, this 
furnishes an excellent basis for estimating refrigeration. 
The generally accepted unit of measure is the ton of refrigera- 
tion, which may be defined as the amount of heat (B. t. u.) which 
one ton of 2000 pounds of ice at S2 degrees, loill absorJ) in melting to 
water at 32 degrees. Since the latent heat of ice is 144 B. t. u. 
per pound, one ton of refrigeration is equal to 288000 B. t. u. 
Just as a pumping plant is rated at a certain number of 
millions of gallons, meaning millions of gallons in twenty- 
four hours, so a refrigeration plant is rated in so many 
tons of refrigeration, meaning- so many tons in twenty-four 
hours. Hence one ton of refrigeration capacity for one day 
is equivalent to 12000 B. t. u. per hour, this value being- the 
unit of refrigerating capacity, sometimes referred to as tonnage 
capacity, or refrigerating effect, and usually designated by T. 

233. Calculation of Required Capacity: — To estimate 
closely the tonnage capacity of a refrigerating- plant for 
any certain store space requires specific attention to supply- 
ing the following losses: 

(a) The radiated and conducted heat entering the 
room. This may be divided into that due to the walls and 
that due to the windows and sky-lights. 

(b) The heat entering by the renewal of the air, or 
ventilation of the enclosed space. This may "be divided into 
heat given off by the air and heat given off due to the 
latent heat of the moisture. 

(c) The heat entering by the opening of doors. 

(d) The heat from the men at work, lights, chemical 
fermentation processes, etc. 

(e) The heat abstracted from material in cold storage. 



REFRIGERATION 



379 



Refrigeration losses due to entrance of radiated and con- 
ducted heat may be calculated by Equations 26, 27 and 28, 
Chapter III, if the proper transmission constants are in- 
serted. To obtain these constants for various types of in- 
sulation use Tables VI and XL. 



TABLE XL. 
Heat Transmission of Standard Types of Dry Insulation. 



Material 


K 


Material 


K 


Mill shavings, Type (a) 
1" thickness __ 


.ia3o 

.1090 
.0920 
.0800 
.0710 
.0630 
.0570 
.0.520 
.0440 
.0390 
.0.340 
.0308 
.0279 
.0255 
.0235 
.0218 


Hair Felt, Type (a) 
1" thickness 


.1.38 


2" 


Vi", V2", Vi", Type (c) 

Sheet Cork, Type (d) 

i" with I" air space 

5" with 1" air space 

3", Type (b) ___ 


.105 


.3" " 




4" " _ ._ 


.050 


5" " _ . . ._ 


.037 


6" " _- _- 


.087 


7" 


1", Type (a) _- 


.137 


8" 


Granulated Cork 
4", Type (a) 




10" " 


.071 


12" " 


Mineral Wool 
2V2" Type (b) 




14" " 


.1.51 


16" " _ - - _- 


1", Type (b) 


.192 


18" " - 


Air Spaces 

8", Type (a) 




20" 


.112 


9.7// a 






24" " 





^TAR PAPER— ^ 
/ 5HAVING55i— A 



TAR PAPLR-N 




In g-eneral any space to be kept at or below zero degrees 
should have insulation allow^ing no greater transmission 
than .04, and for spaces to be kept at from degrees to 30 
degrees no greater transmission should be allowed than .06, 
while for temperatures above 30 degrees a transmission as 
great as .1 is allowable. In any case, however, it should be 



380 HEATING AND VENTILATION 

remembered that the heat loss, and therefore the expense of 
operation, is directly proportional to this factor and the 
best possible insulation, consistent with available building 
funds, is the one to use, the ceiling and floor being as care- 
fully insulated as the walls. Window construction should 
be tight, non-opening, and at least double. 

The refrigeration loss due to ventilation may be considered 
under two heads, i. e., the cooling of the air from the 
higher to the lower temperature, and the cooling, condens- 
ing and freezing- of the moisture in the air. In this par- 
ticular, air cooling cannot be considered exactly the re- 
verse of air w^arming. In air warming the vapor present 
absorbs heat but this vapor has so little heat capacity com- 
pared with that of the air that no noteworthy error is intro- 
duced by ignoring the vapor. However, in air cooling the 
dew point is almost invariably reached and passed, so that 
considerable moisture is changed from the vapor to the 
liquid with a liberation of its heat of vaporization. This is 
considerable and cannot be ignored without serious error. 
If, further, conditions are such that this moisture is frozen, 
its latent heat of freezing must also be accounted for. 
These two items are relatively so large that to cool air 
through a given range of temperature may involve several 
times the heat transfer required to warm the same air 
through the same range of temperature. 

Application. — Assume outside air 95 degrees, relative 
humidity 85 per cent., temperature of air upon leaving cool- 
ing coils 30 degrees and temperature of coil surface 10 de- 
grees. If 180000 cubic feet of air per hour are drawn in 
from the atmosphere, the refrigerating capacity of the coils 
may be obtained as follows. To cool the air from 95 degrees 
to 30 degrees will require (Equation 29), 

180000 X (95 — 30) 
r= 212700 B. t. u. 



55 

At 95 degrees and 85 per cent, humidity one cubic foot of 

air contains, (Table 11, Appendix), .85 X 17.124 = 14.555 

grains of moisture. At 30 degrees and saturation one cubic 

foot of air contains, (Table 11), 1.935 grains. Hence there 

180000 (14.555 — 1.935) 

would be deposited upon the coils '■ = 

7000 

324.5 pounds of moisture per hour. Now there would be 

absorbed from each pound of this moisture 



REFRIGERATION 381 

32 B. t. u. to cool from 95 to 32 degrees. 
1073 B. t. u. to chang-e to liquid form. 
144 B. t. u. to freeze (if allowed to freeze on coils). 
11 B. t. u. to cool from 32 to 10 deg^rees. 

1260 B. t. u. total. 
Hence the coils would have to absorb from the moisture 
alone 1260 X 324.5 —- 408870 B. t. u. per hour, or for both 
moisture and air, 212700 + 408870 = 621600 B. t. u. per hour. 
This indicates, for the ventilation proposed, a tonnag'e capac- 
ity of 621600 ^ 12000 = 51.8 tons of refrig-eration needed at 
the bunker room coils. The above provides that the air is 
rejected at the interior temperature, 30 deg-rees. Modern 
plants, however, would pre-cool the incoming- air before it 
reached the bunker room by having- part of its heat ab- 
sorbed by the outg-oing- 30 deg-ree air, which would reduce 
the estimate somewhat below 51.8 tons. 

In considering- the refrig-eration loss due to the opening of 
(lows no rational method of calculation is applicable, but if 
the nature of the cold storag-e service is such that doors are 
frequently opened, as hig-h as 25 per cent, may be allowed. 
Generally this is taken from 10 to 15 per cent. 

The refrig-eration loss due to persons, lights, etc., may be 
estimated as sug-g-ested in Art. 44. If the cooling air is 
recirculated, the cooling- and freezing- of the moisture g-iven 
off by each person should be taken into account, especially 
if the number is larg-e. For this purpose it is safe to assume 
a maximum of 500 g-rains of moisture g-iven off per person 
per hour when such persons are not eng-ag-ed in active phy- 
sical exercise. 

234. Calculations for Square Feet of Cooling Coil; — This 
problem presents g-reater uncertainty in its solution than 
does the desig-n of a heating- coil surface because of the lack 
of experimental data and because of the variable insulat- 
ing- effect of ice and frost accumulations, if allowed to form. 
Professor Hanz Lorenz in "Modern Refrig-erating- Machin- 
ery," pag-e 349, quotes 4 B. t. u. per square foot per hour per 
deg-ree difference between the averag-e temperatures on the 
inside and outside of the coils, as a safe designing: value 
when the air speed is 1000 feet per minute over the coils. 
This is for plants in continuous operation, as abattoirs, cold 
stores and in places where no provision is made against ice 



382 HEATING AND VENTILATION 

formation. For clean pipe surface in the plenum air cooling 
plant of the New York Stock Exchange Building- the heat 
transmission is approximately 430 B. t. u. per square foot 
per hour with air over coils at 1000 feet per minute. Under 
the average temperatures there used, this corresponds to a 
transmission per degree difference per square foot per hour 
of approximatel3^ 7 B. t. u. These two values, 4 and 7, may- 
be taken as about the minimum and maximum transmission 
constants for plenum cooling coil installations. 

For direct cooling coils, where the pipe surface is sim- 
ply exposed to the air of the room to be cooled, Lorenz 
recommends a transmission allowance of not over 30 B. t. u. 
per square foot per hour, for in such installations the re- 
moval of ice and frost is seldom contemplated. For an aver- 
age room temperature of 30 degrees and average brine tem- 
perature of 10 degrees, this would correspond to 30 ^ 20 =i 
1.5 B. t. u. transmitted per square foot per hour per degree 
difference. 

Application 1. — How many lineal feet of 1^4 inch direct 
refrigerating coils \\^ould be required to keep a cold stor- 
age room at 30 degrees if the refrigeration loss is 80000 
B. t. u. per hour total and the temperatures of the brine en- 
tering and leaving the coils are 10 degrees and 20 degrees 
respectively? Average brine temperature = 15 degrees. Al- 
lowing a transmission constant of 1.5, Equation 51 becomes, 

H 

Rr = ■ = — .0445 H 

1.5 (15 — 30) 

For this problem we have .0445 X 80000 = 3500 square feet, 

or 3500 X 2.3 = 8050 lineal feet of 1^4 inch pipe. 

Application 2. — The cooling of 180000 cubic feet of air per 
hour in Art. 233 required the extraction of 621600 B. t. u. per 
hour. Determine the plenum cooling surface required, if 
brine enters at degrees and leaves at 20 degrees. 

Average brine temperature = 10 degrees. Assuming 

that there is provision for keeping coils clear of ice, and 

hence a transmission constant of 7 B. t. u. is allowable. 

Equation 65 gives 

621600 
Rr = = — 1691 square feet of surface. 

r95 + 30 \ 
10 I 



REFRIGERATION 383 

The negative sign indicates a flow of heat in the direc- 
tion opposite to the flow in heating- installations, for which 
the equation was primarily designed. 

235. General Application: — Considering- the school build- 
ing and the table of calculated results as given in Art. 155, 
what ainount of cooling coil surface would be required to 
keep the temperature of all rooms of this building at 73 
degrees on a day when the outside air temperature is 95 
degrees and the relative humidity 85 per cent.? 

Data Table XXXV gives the total heat loss of the three 

floors of this building as 1483250 B. t. u. per hour on a zero 

day when the rooms are kept at 70 degrees. Now this same 

building under the summer conditions would have delivered 

to it heat due to a temperature difference of 95 degrees — 73 

degrees = 22 degrees. Hence the total refrigeration loss dur- 

22 

ing the summer day would be approximately X 1483250 = 

70 

466000 B. t. u. per hour, which amount of heat would be used 
to warm the incoming air from some temperature up to 73 
degrees. Suppose the ventilation requirement of the build- 
ing is 2000000 cubic feet per hour. Since it requires 1/55 of 
a B. t. u. to warm one cubic foot of air one degree, [2000000 
(73 — *)] -f- 55 r= 466000, or t = 60.2, say 60 degrees. (See 
Arts. 50 and 51 and observe that the second term of the right 
hand member of Equation 36 becomes a negative term). 

While the air is traversing the ducts between the coils 
and the rooms, allow a rise in temperature of 5 degrees. 
The coils vv^ould then be required to deliver 2000000 cubic 
feet of air per hour at 55 degrees when supplied with air at 
90 degrees and 85 per cent, humidity. To cool this amount 
of air through the given range would require the absorption 
of (Equation 29) [2000000 X (95 — 55)] ^ 55 = 1454500 B. t. u. 
At 95 degrees and 85 per cent, humidity, 1 cubic foot of air 
contains (Table 11), .85 X 17.124 = 14.555 grains of moisture. 
At 55 degrees and saturation point, 1 cubic foot of air con- 
tains (Table 11), 4.849 grains of moisture. Hence, neglecting 
change in air volume, there would be deposited on the coils 
approximately [2000000 (14.555 — 4.849)] -^ 7000 = 2775 
pounds of moisture per hour. 

Now, if an average brine temperature of 10 degrees is 
used and provision is made for keeping the coils clear of ice, 
the condensation will leave at some temperature above 10 



384 HEATING AND VENTILATION 

degrees, say 20 degrees, and there will be absorbed from 
each pound of this moisture approximately 

20 B. t. p. to cool from 95 to 55 degrees. 
1061 B. t. p. to change to liquid form at 55 degrees. 

35 B. t. u. to cool the water from 55 to 20 degrees. 

1116 B. t. u. total. 
Hence the coils would have to absorb from moisture alone, 
2775 X 1116 = 3096900 B. t. u., or from both moisture and air 
a total of 1454500 + 3096900 = 4551400 B. t. u. per hour. At 
an allowed rate of transmission of 7 B. t. u. there would be 
required to cool this building a total of approximately 9100 
square feet of coil surface, under the conditions of ventila- 
tion as assumed. 

It should be noted that whereas less than 3000 square feet 
of plenum surface were sufficient to heat the building ac- 
cording to Application 2, Art. 137, it requires fully three 
times this amount of surface in cooling coils to cool the 
building under the assumed conditions. Upon inspection it 
is seen that the greatest work of the cooling coils is the 
condensation and cooling of the moisture. 

The relative humidity within the cooled rooms would be 

approximately 55 per cent., for the content per cubic foot of 

incoming air is 4.849 grains, and the capacity of the air 

when heated to 73 degrees is 8.782 grains showing a relative 

4.849 

humidity, after heating, of = 55 per cent. This would 

8.782 

be raised somewhat by the persons present. 

336. Ice Making Capacity. Calculation: — Neglecting 

losses, the ice making capacity of a refrigerating plant for 

a certain refrigeration tonnage may be expressed 

144 T 



I = (132) 

(f— 32) + 144 + .5 (32 — ii) • 

in which / = tons of ice produced per 24 hours, T = refrig- 
eration tonnage or rating of plant, t = initial temperature of 
water and tx = final temperature of ice, usually 12 to 18 
degrees. 

Application. — What should be the ice making capacity of 
a plant having a tonnage rating of 100, if t = 70 degrees and 
/i = 16 degrees? Take losses at 35 per cent. 

.65 X 144 X 100 
/ =r =z 49.3 tons in 24 hours. 



(70 — 32) + 144 + ,5 (32 — 16) 



REFRIGERATION 385 

237. Gallon Degree Calculation: — For use in plants pro- 
ducing ice by brine circulation a unit called the gallon degree 
is sometimes used. It represents a change of one degree 
temperature in 1 gallon of brine in one minute of time. It 
is not a fixed unit representing a constant number of 
B. t. u., since the brine strength, and therefore its specific 
heat, may vary. The value in B. t. u. per minute, of a gallon 
degree for any plant may be obtained by multiplying the 
specific gravity of the brine by its specific heat and by 8.35, 
the weight of one gallon of water, or as an equation may be 
stated 

D = 8.35 gJi (133) 

where D = B. t. u. per minute equal to one gallon degree, 
g = specific gravity of brine and h = specific heat of brine. 
The numher of gallon degrees per ton of refrigerating capacity 
may be found by dividing 200 by D, since one ton of refrig- 
erating capacity is equal to 200 B. t. u. per minute, then 

200 24 • ,. 

Dt = = for all practical purposes. (134) 

8.35 gh gh 

The refrigerating capacity of a given hrine circulation may be 

obtained by dividing the product of the gallons circulated 

and the rise in brine temperature by the value Dt. Stated 

as an equation this is 

0{t. — t->) ghGif., — 1^) 

T - = (135) 

Bt 24 

where T = tonnage capacity, G = gallons of brine circu- 
lated per minute and (tz — t^) = rise of brine temperature. 

238. Refrigerating- Capacity of Brine Cooled Sy.stem: — 

To calculate the capacity but two things are required, the 
amount of brine circulated, and the rise in temperature of 
the brine. From these the capacity may be obtained by 
the equation 

Wh (to — ts) 

T - ■ (136) 

12000 

where T = tonnage capacity, TF = weight of brine circulated, 

in pounds, h = specific heat of brine and (/o — to) zn rise in 

temperature of brine. 

239. Cost of Ice Making and Refrigeration: — The cost of 
ice manufacture is affected principally by the following 
items: price and kind of fuel, kind of water, cost of labor, 
regularity of operation, method of estimating costs, etc. 



386 ^ HEATING AND VENTILATION 

It is found in practice to range anywhere from $0.50 to 
$2.50 per ton. The items making- up the cost of ice manu- 
facture are: fuel for power, labor at the plant, water, am- 
monia and minor supplies, maintenance of the plant, inter- 
est and taxes, and administration. Mr. J. E. Siebel in his 
"Compend of Mechanical Refrigeration and Engineering" 
gives an itemized account of the daily operating expense of 
a 100-ton plant with which he was connected, the plant 
operating 24 hours per day. 

Chief engineer ..$ 5.00 

Assistant engineers 6.00 

Firemen 4.00 

Helpers 5.00 

Ice pullers ." 9.00 

Expenses 12.00 

Coal at $1.10 per ton 18.00 

Delivery (wholesale) 50c per ton 50.00 

Repairs, etc 3.00 

Insurance, taxes, etc 6.00 

Interest on capital 20.55 



Total for 100 tons of ice $138.55 

The length of time that the ice is permitted to freeze 
is a factor affecting the cost of production. The following 
figures are given for a 10-ton plant: 

Engineer 

Fireman 

Tankmen, helpers .... 

Coal 

Repairs, supplies, etc, 

Total for 10 tons $10.00 $15.50 

Mr. A. P. Criswell, in "Ice and Refrigeration," gives the 
following approximate costs for the production of can ice 
per ton with coal at $2.50 per ton and with a simple distill- 
ing system. The figures are for the plant operating at full 
capacity and do not include cost of administration. 



Ten tons 

n 12 hours 

$2.50 


Ten tons 
in 24 hours 

$5.00 


1.50 


3.00 


1.50 


3.00 


3.00 


3.00 


1.50 


1.50 



REFRIGERATION 387 

Capacity of plant Cost per ton 

10 tons $1.58 

20 " 1.48 

30 " 1.42 

40 " 1.38 

50 " 1.36 

70 " 1.34 

100 " 1.34 

120 " 1.30 

Mr. Karl Wegemann states that a certain moderate sized 
plant of the absorption system produced ice for a number 
of years at an averag-e cost of $0.85 por ton after allowing 
for melting- and breakage. This included all charges ex- 
cept for interest, insurance and administration. 

The following figures taken from the books of another 
plant show clearly the effect of demand upon the cost of 
manufacture. 

Month Cost per ton 

January $3.50 

February 3.70 

March 2.80 

April 2.17 

May 1.75 

June 1.19 

July 1.02 

August 1.02 

September 1.03 

October 1.26 

November 2.10 

December 2.94 



CHAPTER XVIII. 



PLANS AND SPECIFICATIONS FOR HEATING SYSTEMS. 



In Planninj^ for and Executing Engineering Contracts, 

the responsibilities assumed by the various interested parties 
should be thoroug"hly studied. The following- outline shows 
the relationship between these parties and the order of the 
responsibility. 

/Engineer. 
Owner t 

I Superintendent and Inspector, 
or < 

\ General contractor, Subcontractors,-Foremen and 
Purchaser I ^^ -, 

\ Workmen. 

The engineer, the superintendent and the general con- 
tractor occupy positions of like responsibility with relation 
to the purchaser. The first two -work for the interest of the 
purchaser to obtain the best possible results for the least 
money, and the last endeavors to fulfill the contract to the 
satisfaction of the superintendent, at the least possible ex- 
pense to himself. These points of view are quite different 
and sometimes are antagonistic, but both are right and just. 
Of the three parties, the engineer has the greatest respon- 
sibility. It is his duty to draw up the plans and to write 
the specifications in such a way that every point is made 
clear and that no question of dispute may arise between the 
superintendent and the contractor. His plans should detail 
every part of the design with full notes. His specifications 
should explain all points that are difficult to delineate on the 
plans. They should give the purchaser's views covering all 
preferences, and should definitely state where and what ma- 
terials may be substituted. Where any point is not definitely 
settled and left to the judgment of the contractor, he may 
be expected to interpret this point in his favor and use the 
cheapest material that in his judgment will give good re- 
sults. This opinion may differ from that held by the pur- 
chaser. All parts should be made so plain that no two opin- 
ions could be liad on any important point. The engineer 



TYPICAL SPECIFICATIONS 389 

should also be careful that the plans and specifications agree 
in every part. The inspector is the superintendent's repre- 
sentative on the g-rounds and is supposed to inspect and 
pass upon all materials delivered on the g-rounds, and the 
quality of workmanship in installing. For such information 
see Byrne's "Inspector's Pocket-Book." The general con- 
tractor usually sublets parts of the contract to subcon- 
tractors who work through the foreman and workmen to 
finish the work upon the same basis as the general con- 
tractor. 

The follow^ing brief set of specifications are not con- 
sidered complete but are merely inserted to suggest how 
such work is done." 

Typical Specifications. 
Title Page : — 

SPECIFICATIONS 

for the 

MATERIALS AND WORKMANSHIP 

Required to Install 



(Type of system) 

HEATING AND VENTILATING SYSTEM 

in the 



(Building) 



(Location) 
by 



(Name of designer) 
Index Page : — 

(To be compiled after the specifications are written.) 

General Remarks to Contractor. — In the following specifica- 
tions, all references to the Owner or Purchaser will mean 

or any person or persons delegated by 

to serve as the representative. The Super- 
intendent of Buildings will be the purchaser's representative at 
all times, unless otherwise definitely stated. The contractor 
will, therefore, refer all doubtful questions or misunder- 
standings, if any, to the superintendent whose decision will 
be final. In case of any doubt concerning- the meaning of 



390 HEATING AND VENTILATION 

any part of the plans or specifications, the contractor shall 
obtain definite interpretation from the superintendent be- 
fore proceeding- with the work. 

These specifications with the accompanying- plans and 

details (sheets to inclusive) cover the purchase of 

all the materials as specified later (the same materials to 
be new in every case), and the installation of the same in a 
first class manner within the above named building, located 
at (street) "... (city) (state). 

It will be understood that the successful bidder, herein- 
after called the contractor, shall work in conformity with 
these plans and specifications and shall, to the best of his 
ability, carry out their true intent and meaning. He shall 
purchase and erect all materials and apparatus required to 
make the above system complete in all its parts, supplying 
only such quality of materials and workmanship as will har- 
monize w^ith a first class system and develop satisfactory 
results when working under the heaviest service to which 
such plants are subjected. 

The contractor shall lay out his own work and be re- 
sponsible for its fitting to place. He shall keep a competent 
foreman on the grounds and shall properly protect his work 
at all times, making good any damage that may come to it, 
or to the building, or to the work of other contractors from 
any source whatsoever, which may be chargeable to himself 
or to his employees in the course of their operations. 

Any defects in materials or workmanship, other than 
as stated under — (state exceptions if any) — that may develop 
within one year, shall be made good by the contractor upon 
written notification from the purchaser without additional 
cost to the purchaser. 

The contractor shall, wherever it is found necessary, 
make all excavations and back-fill to the satisfaction of the 
superintendent. 

The contractor shall be responsible for all cuttings of 
wood work, brick work or cement work, found necessary 
in fitting his materials to place, either within or without the 
building; the cutting to be done to the satisfaction of the 
superintendent. The contractor shall be required to connect 
and supply water and gas for building purposes, and shall 
assume all responsibility for the same. 



TYPICAL SPECIFICATIONS 391 

The contractor shall be required to protect the purchaser 
from damage suits, originating- from personal injuries re- 
ceived during the progress of the work; also, from actions 
at law because of the use of patented articles furnished by 
the contractor; also, from any lien or liens arising because 
of any materials or labor furnished. 

The purchaser reserves the right to reject any or all 
bids. 

No changes in these plans and specifications will be 
allowed except upon written agreement signed by both the 
contractor and the purchaser's representative. 

System. — Specify the system of heating in a general way; 
high pressure, low pressure or vacuum; direct, direct-indi- 
rect or indirect radiation; basement or attic mains; one- or 
two-pipe connections to radiators. If ventilation is provided, 
state the movement of the air and the general arrangement 
of fans, coils or other heating surfaces. Single or double 
duct air lines, etc. 

Boilers. — Specify type, number, size and capacity, steam 
pressure, approximate horse-power, heating surface, grate 
surface and kind of coal to be used. Locate on plan and ele- 
vation. Explain method of setting, portable or brick. 
Specify also, flue connection, heating and water pipe connec- 
tions, kind of grate, thermometers, gages, automatic damper 
connection, firing tools and conditions of final tests. 

Conduits and Conduit Mains. — (In this it is assumed that the 
boilers are not within the building). In addition to the lay- 
out, give sections of the conduit on plans showing method 
of construction, supporting and insulating pipes, and drain- 
age of pipes and conduits. Specify quality and size of mate- 
rials, pitch and drainage of pipes and all other points not 
specially provided for in the plans. 

AncJiors. — Locate and draw on plans and specify for the 
installation regarding quality of materials. 

Expansion Joints or Take-ups. — Locate and draw on plans. 
Select type of joint and specify for amount of safe take-up 
and for quality of material. 

Mains and Returns. — Trace the steam from the point where 
nt enters the main, through all the special fittings of the 

system. Show where the condensation is dripped 

to the returns through traps or separating devices. Specify 
amount and direction of pitch, kind of fittings (flanged or 



392 HEATING AND VENTILATION 

screwed, cast iron or malleable iron), kind of corners (long 
or short), method of taking up expansion and contraction. 
Trace returns and specify dry or wet. 

Branches to Risers. — Take branches from top of mains by 
tees, short nipples and ells, and enter the bottom of the 
risers by sufficient inclination to g-ive good drainage. 

Risers. — Locate risers according to plan. They shall be 
straight and plumb and shall conform to the sizes given on 
the plans. No riser shall overlap the casing around win- 
dows. State how branches are to be taken off leading to 
radiators, relative to the ceiling or floor. 

Radiator Connections. — Specify, one-pipe or two-pipe, num- 
ber and kind of valves, sizes of connections and hand or 
automatic control. All connections shall allow for good 
drainage and expansion. Distinguish between wall radiator 
and floor radiator connections. If automatic control is used, 
hand valves at the radiators are usually omitted. 

Radiators. — Specify floor or wall radiators, with type, 
height, number of columns and number of sections. If other 
radiators are substituted for the ones that are referred to 
as acceptable, they must be of equal amount of surface and 
acceptable to the superintendent. Specify brackets for wall 
radiators, also, air valves for all radiators, stating type 
and location on the radiator. Require all radiators to be 
cleaned with water or steam at the factory and plugged at 
inlet and outlet for shipment. 

Piping. — Define quality, weight and material in all mains, 
branches and risers. All sizes above one and one-half inch 
are usually lap welded. Piping should be stood on end and 
pounded to remove all scale before going into the system. 
All pipes 1 inch and smaller should be reamed out full size 
after cutting. 

Fittings. — Specify quality of fittings, whether light, stand- 
ard or heavy, malleable or cast iron. Fittings with imper- 
fect threads should be rejected. 

Yalves. — Specify type (globe, gate or check), whether 
flanged or screwed, rough or smooth body, cast iron or 
brass, and give pressure to be carried. All valves should 
be located on the plans. 

Expansion Tank. — Specify capacity of tank in gallons, kind 
of tank (square or round, wood or steel), method of connect- 
ing up with flttings and valves, and locate definitely on plan 



TYPICAL SPECIFICATIONS 393 

and elevation. Connect also to fresh water supply and to 
overflow. 

Hangers and Ceiling Plates. — ^Wall radiators and horizontal 
runs of pipe shall be supported on suitable expansion hang- 
ers or wall supports that will permit of absolute freedom of 

expansion. Supports shall be placed feet centers. Pipe 

holes in concrete floors shall be thimbled. Holes through 
wooden walls and floors shall have suitable air space around 
the pipe, and all openings shall be covered with ornamental 
floor, ceiling or wall plates. 

Traps. — Specify type, size, capacity and location. State 
whether flanged or screwed flttings are used and whether 
by-pass connection will be put in. Refer to plans. 

Pressure Regulating Valve. — Specify type, size and location, 
also maximum and niinimum steam pressure, with guaran- 
tee to operate under slight change of pressure. State if 
by-pass should be used and explain with plans. 

Separators. — Specify type (horizontal or vertical), also 
size and location. 

Automatic Control. — The contractor will be held responsible 
for the installation of all thermostats, regulator valves, air 
compressor, piping and flttings required to equip ail roomxS 
and halls with an automatic temperature control sys- 
tem. Specify approximate location and number of thermo- 
stats with the desired flnish. Specify in a general way, reg- 
ulator valves on radiators, quality of pipe, maximum test 
pressure for pipe, power for air supply (hydraulic, pneu- 
matic, etc.), and supply tank. All materials in the tem- 
perature control system shall be guaranteed first class by 
the manufacturer through the contractor, and the system 
shall be guaranteed to give perfect control for a period of 
(two) years. 

Fans. — Specify for direct connected or belt driven, right 
or left hand, capacity, size, housing, direction of discharge, 
horse-power, R. P. M. and pressure. State in a general w^ay 
the requirements of the fan wheel, steel plate housing, shaft, 
bearings and the method of lubrication. 

Engine. — Specify type, horse-power, steam pressure, ap- 
proximate cut-off, speed and kind of control. 

Electric Motors. — Specify type, horse-power, voltage, cycles, 
phases and R. P. M. 



394 HEATING AND VENTILATION 

Indirect Heating Surface. — Specify the kind of surface to 
be put in and then state the total number of square feet 
of surface, with the width, heig-ht and depth of the heater. 
State definitely how the heaters will be assembled, giving 
free height of heater above the floor. Describe damper con- 
trol, steam piping to and from heater, housing around heater, 
connection from cold air inlet to heater and connection from 
heater to fan. See plans. The contractor will usually follow 
installation instructions given by the manufacturers for the 
erection of the heater and engine, consequently the specifi- 
cations should bear heavily only upon those points which 
may be varied to suit any condition. All valves, piping and 
fittings in this work should be controlled by the general 
specifications referring to these parts. 

Foundations. — Specify materials and sizes. 

Air Ducts, Stacks and Galvanized Iron Work. — The drawings 
should g-ive the layout of all the air lines, giving connections 
bet"ween the air lines and the fan, and the air lines and the 
registers. Where these air lines are below the floor, the 
conduit construction should be carefully noted. All gal- 
vanized iron work should be shown on the plans and the 
quality and weight should be specified. Air lines should 
have long- radius turns at the corners. 

Registers. — Specify height above fioor, nominal size of 
register, method of fitting in wall, the finish of the regis- 
ter and whether fitted with shutters or not. 

Protection and Covering. — Specify kind and quality of pipe 
covering and the finish of the surface of the covering. State 
the amount of space between heating- pipes and unprotected 
woodwork. Distinguish between pipes that are to be covered 
and those that are to be painted. All radiators and piping 

not covered should be painted with two coats of bronze 

or other finish acceptable to the superintendent. 

Cofnpletion. — Require all rubbish removed from the build- 
ing and immediate grounds and deposited at a definite place. 



SUGGESTIOIVS TO SCHOOL DISTRICTS. 



It frequently happens that School Boards and School 
Trustees are required to select from a number of proposed 
heating- and ventilating- systems that one which is best 
suited to their needs. Public officials, as a rule, are not ex- 
pected to be engineers and occasionally make a selection 
which afterward proves to be a misfit. The following sug- 
gestions, therefore, are offered in the hope that some men 
may be benefited thereby. 

DEFINITIONS. 

Radiating surfaces. — Radiators, coils and stoves. 

Circulating air. — Air which passes over the radiating 
surfaces and carries heat to the rooms. This may be outside 
air or returned air from the rooms. 

Ventilating air. — Circulating air taken from without the 
building-. 

Dii-ect system. — Radiating surfaces set within the rooms 
to be heated. No special outside air connections. 

Indirect system. — Radiating surfaces set in the basement 
or somewhere within the building and below the rooms to be 
heated. Air is passed over these radiating surfaces, heated 
and carried through ducts to the rooms. "When this air is 
taken from without the building there is provision for good 
ventilation. 

Direct-indirect system. — Radiating surfaces set within 
the rooms to be heated, usually next the outside wall, and 
supplying ventilating- air for the rooms by means of short 
ducts through the walls. A fair quality of ventilation may 
be obtained under favorable conditions. 

One-pipe steam system. — Radiators connected at one bot- 
tom end only. This serves both for steam inlet and con- 
densation return. Air valves are a necessity and are located 
about mid-height on the last coil of the radiator. 

Two-pipe steam system. — Radiators double connected; 
bottom for return, and top or bottom for steam. Where top- 
connected for steam, use water-type radiator only. Air 
valves useful but not as necessary as on one-pipe system. 

Low-pressure steam system. — Steam circulated by grav- 
ity at pressures between and 5 pounds gage. 

Atmospheric and vapor systems. — Steam circulated by 
gravity at to 0-pressures. Radiators always two-pipe, 
water-type, top-connected for steam. Graduated inlet valve. 
Air valves on end of return. 

Meclianical vacuum systems. — Steam pressures to 5 
pounds gage. Condensation returned by pump below atmos- 



pheric pressure. Circulation positive. Returns sinaller than 
gravity returns. Air valve on return tank. 

Gravity room-heater system. — Large metal-encased 
stoves set within the rooms to be heated and circulating' 
room air or outside air upward between the stove and cas- 
ing, thus heating it for room use. When the air is partially 
or wholly taken from the outside of the building, this heater 
makes a direct-indirect system. 

Aspirating- vent flues. — Smooth vertical flues containing 
heating coils and leading to the outside air through the 
roof. These flues should be located in the partition walls 
of the building. The heating coils create ascending cur- 
rents of air within the flues and assist room ventilation. 

Cowls. — Metal cappings on the tops of the ventilating 
flues, so constructed as to assist convection currents within 
the flues and prevent down drafts. 

Gravity warm-air furnace system. — A large metal- or 
brick-encased stove, usually set in the basement, and having 
one or more circulating air pipes leading into and from the 
space between the stove and the casing. Circulation is main- 
tained wholly by the difference in weight (density) between 
the warmer air at the furnace and that of the cooler sur- 
rounding atmosphere. The entire circulating air may be re- 
turned from the rooms to the furnace, in which case there 
is no ventilating effect; or, a part of the air may be recir- 
culated with part taken from the outside, giving some ven- 
tilating effect; or, all the air may be taken from the out- 
side, with the best ventilating- effect. All furnace systems 
should have outside air connections of such size as will per- 
mit all the air to be taken from the outside. 

Fan-furnace systems. — A hot air furnace, similar in prin- 
ciple to the gravity warm-air furnace, with blower attach- 
ment. Circulating air temperatures generally higher than 
those of the warm-air furnace system. 

Fan-coil system. — Metal-encased steam-coils as heating 
surfaces, with air circulation over the coils maintained by 
blower attachment. Best ventilating possibilities. Circulat- 
ing air temperatures about the same as in the gravity warm- 
air furnace system. 

"Ventilating systems. — These may be either independent 
of or a part of the heating system. The air supply for ven- 
tilation shall be from an uncontaminated source, or shall be 
air from which the dust or other impurities shall be removed 
by efficient air cleansing devices. Circulation may be pro- 
duced by gravity, in which case the air movement is slug-. 



SUGGESTIONS TO SCHOOL DISTRICTS 397 

gish and the ducts and stacks necessarily large; or by 
mechanical means, resulting in higher air velocities and 
correspondingly smaller ducts and stacks. Positive air cir- 
culation in vent stacks is very important in all gravity air 
circulating plants. Where electric power is available, me- 
chanical circulation by fans is the most satisfactory and is 
the least expensive system to operate. Where power is not 
available, circulation may be obtained by the use of aspirat- 
ing coils and cowls. Although aspiration is a wasteful pro- 
cess, it is practically fool-proof. In large plants where the 
exhaust steam may be used in coils for heating, steam en- 
gine-driven fans for the air supply are more economical than 
electric drives. Gas engine drives are noisy and unreliable 
and should be used in school systems only as a last resort. 

CLASSIFICATION OP SYSTEMS. 

The following classification is suggestive only, and is 
intended as an aid to show those systems best adapted to 
the different types of school buildings. 
One-room building, no basement. 

Direct-indirect room-heater. 
One-room building:, with basement. 

Gravity furnace system. 

Indirect, one-pipe or two-pipe steam system. 

Direct-indirect, one-pipe or two-pipe steam system. 
T^vo-room building-, one floor, no basement. 

Direct-indirect room heater in each room. 
T^vo-room building, one floor, with basement. 

Gravity furnace system with vent flues and cowls. 

Indirect, one-pipe or two-pipe steam system with as- 
pirating vent flues and cowls. 

Direct-indirect, one-pipe or two-pipe steam system, with 
aspirating vent flues and cowls. 
Three-room building, one floor, with basement. 

Gravity furnace system with vent flues and cowls. 

Indirect, one-pipe or two-pipe steam system, with as- 
pirating vent flues and cowls. 

Direct-indirect, one-pipe or two-pipe steam system, with 
aspirating vent flues and cowls. 
Four-room building, two floors, with basement. 

Gravity furnace system with vent flues and cowls. 



398 HEATING AND VENTILATION 

Indirect or direct-indirect steam systems, with aspirat- 
ing vent flues and cowls. 

Fan furnace system (where electric power is available). 
Automatic temperature control. 

Four-room building', two floors ^vith basement rooms used 
for school purposes bixt not as laboratories or class 
rooms. 

Indirect or direct-indirect steam system on first and sec- 
ond floors, and direct system in basement; with aspirating 
vent flues and cowls. With or without automatic tempera- 
ture control. 

Fan-furnace system (where electric power is available). 
Automatic temperature control. 

Six- or eight-room building, with basement rooms used foi* 
laboratory and school purposes other than class rooms. 

Fan-coil system, with electric power or low-pressure 
steam engine. Direct radiation in corridors, toilet and wash 
rooms. Automatic temperature control. Toilets separately 
ventilated by motor driven suction fans. 

Direct-indirect, vapor or low-pressure steam system on 
first and second floors, and direct system in the basement; 
with aspirating- vent flues and cowls. With or without auto- 
matic temperature control. 

Fan-furnace system (where electric power is available). 
Automatic temperature coiTtrol. Toilets separately venti- 
lated by motor driven suction fans. 
Moderately large buildings Avith basement school rooms. 

Heat by direct radiation, mechanical vacuum returns; 
ventilate by fan-coil system. With or without air condition- 
ing apparatus. Toilets separately ventilated by motor driven 
suction fans. Automatic temperature control. 

Heat and ventilate by fan-coil system. With or without 
air conditioning apparatus. Toilets separately ventilated by 
niotor driven suction fans. Automatic temperature control. 
Large buildings Avith basement school rooms. 

Heat by direct radiation, mechanical vacuum returns, 
ventilate by fan-coil system. Air conditioning apparatus. 
Toilets separately ventilated by motor driven suction fans. 
Automatic temperature control. 

Heat and ventilate by fan-coil system. Air conditioning 
apparatus. Toilets separately ventilated by motor driven 
suction fans. 



APPENDIX 
I. 



GENERAL TABLES. 
HEATING AND VENTILATION. 



Tables in body of text are numbered in Roman 
numerals, those in the Appendixes are numbered in 
Arabic numerals. 

All tables that are not considered general are credited 
and added by permission of the authors. 



TABLE 1. 
Squares, Cubes, Sq. Roots, Cube Roots, Circles. 













Circle 


No. 


Square 


Cube 


Sq. 


Cube 










Diam. 






Root 


Root 


Cireumf. 


Area 


.1 


.010 


.001 


.316 


.464 


.314 


.00785 


.2 


.040 


.008 


.447 


.585 


.628 


.03146 


.3 


.090 


.027 


.548 


.669 


.942 


.07069 


.4 


.160 


.064 


.633 


.737 


1.257 


.12566 


.5 


.250 


.125 


.707 


.794 


1.570 


.19635 


.6 


.360 


.216 


.775 


.843 


1.885 


.28274 


.7 


.490 


.343 


.837 


.888 


2.200 


.38485 


.8 


.640 


.512 


.894 


.928 


2.513 


.50266 


.9 


.810 


.729 


.949 


.965 


2.830 


.63620 


1.0 


1.000 


1.000 


1.000 


l.OOO 


8.1416 


.7854 


1.1 


1.210 


1.331 


1.0488 


1.0323 


3.456 


.9503 


1.2 


1.440 


1.730 


1.0955 


1.0627 


3.770 


1.1310 


1.3 


1.690 


2.197 


1.1402 


1.0914 


4.084 


1.3273 


1.4 


1.960 


2.744 


1.1832 


1.1187 


4.398 


1.5394 


1.5 


2.250 


3.375 


1.2247 


1.1447 


4.712 


1.7672 


1.6 


2.560 


4.096 


1.2649 


1.1696 


5.027 


2.0106 


1.7 


2.890 


4.913 


1.3038 


1.1935 


5.341 


2.2698 


1.8 


3.240 


5.832 


1.3416 


1.2164 


5.655 


2.5447 


1.9 


3.610 


6.859 


1.3784 


1.2386 


5.969 


2.&353 


2.0 


4.000 


8.000 


1.4142 


1.2599 


6.283 


3.1416 


2.1 


4.410 


9.261 


1.4491 


1.2806 


6.597 


3.4636 


2.2 


4.840 


10.648 


1.4832 


1.3006 


6.912 


3.8013 


2.3 


5.290 


12.167 


1.5166 


1.3200 


7.226 


4.1548 


2.4 


5.760 


13.824 


1.5492 


1.3389 


7.540 


4.52.39 


2.5 


6.250 


15.625 


1.5811 


1.3572 


7.854 


4.9087 


2.6 


6.760 


17.576 


1.6125 


1.3751 


8.168 


5.3093 


2.7 


7.290 


19.683 


1.6432 


1.3925 


8.482 


5.72.56 


2.8 


7.840 


21.952 


1.6733 


1.4095 


8.797 


6.1575 


2.9 


8.410 


24.389 


1.7029 


1.4260 


9.111 


6.6052 


3.0 


9.000 


27.000 


1.7321 


1.4422 


9.425 


7.0688 


3.1 


9.610 


29.791 


1.7607 


1.4581 


9.739 


7.. 5477 


3.2 


10.240 


32.768 


1.7889 


1.4736 


10.0-53 


8.0425 


3.3 


10.890 


35.937 


l".8166 


1.4888 


10.367 


8.5530 


3.4 


11.560 


39.304 


1.8439 


1.5037 


10.681 


9.0792 


3.5 


12.250 


42.875 


1.8708 


1.5183 


10.996 


9.6211 


3.6 


12.960 


46.656 


1.8974 


1.5326 


11.310 


10.179 


3.7 


13.690 


50.653 


1.9235 


1.5467 


11.624 


10.752 


3.8 


14.440 


54.872 


1.9494 


1.5605 


11.938 


11.341 


3.9 


15.210 


59.319 


1.9748 


1.5741 


12.252 


11.946 


4.0 


16.000 


64.000 


2.0000 


1.5870 


12.566 


12.. 566 


4.1 


16.810 


68.921 


2.0249 


1.6005 


12.881 


13.203 


4.2 


17.640 


74.088 


2.0494 


1.6134 


13.195 


13.854 


4.3 


18.490 


79.507 


2.0736 


1.6261 


13.509 


14.522 


4.4 


19.360 


85.184 


2.0976 


1.6386 


13.823 


15.205 



400 













Circle 


No. 


Square 


Cabe 


Sq. 


Cube 










Diam . 






Root 


Root 


Cireumf. 


Area 


4.0 


20.250 


91.125 


2.1213 


1.6510 


14.137 


15.904 


4.6 


21.160 


97.336 


2.1448 


1.6631 


14.451 


16.619 


4.7 


22.090 


103.823 


2.1680 


1.6751 


14.765 


17.349 


4.8 


23.040 


110.592 


2.1909 


1.6869 


15.080 


18.096 


4.9 


24.010 


117.649 


2.2136 


1.6985 


15.394 


18.8.59 


5.0 


25.000 


125.000 


2.2361 


1.7100 


15.708 


19.635 


5.1 


26.010 


132.651 


2.2583 


1.7213 


16.022 


20.428 


5.2 


27.040 


140.608 


2.2804 


1.7325 


16.336 


21.237 


5.3 


2s.(m 


148.877 


2.3022 


1.7435 


16.650 


22.062 


5.4 


29.160 


157.464 


2.3238 


1.7544 


16.965 


22.902 


5.5 


30.250 


166.375 


2.3452 


1.7652 


17.279 


23.758 


5.6 


31.. 360 


175.616 


2.3664 


1.7760 


17.593 


24.630 


5.7 


32.490 


185.193 


2.3875 


1.7863 


17.907 


25.518 


5.8 


33.640 


195,112 


2.4083 


1.7967 


18.221 


26.421 


5.9 


34.810 


205.379 


2.4290 


1.8070 


18.536 


27.340 


6.0 


36.000 


216.000 


2.4495 


1.8171 


18.850 


28.274 


6.1 


37.210 


226.981 


2.4698 


1.8272 


19.164 


29.225 


6.2 


38.440 


238.328 


2.4900 


1.8371 


19.478 


30.191 


6.3 


39.690 


2.50.047 


2.5100 


1.8469 


19.792 


31.173 


6.4 


40.960 


262.144 


2.5298 


1.8566 


20.106 


32.170 


6.5 


42.250 


274.625 


2.5495 


1.8663 


20.420 


33.183 


6.6 


43.560 


287.496 


2.5691 


1.8758 


20.735 


34.212 


6.7 


44.890 


300.763 


2.5884 


1.8852 


21.049 


35.2.57 


6.8 


46.240 


314.432 


2.6077 


1.8945 


21.363 


36.317 


6.9 


47.610 


328.509 


2.6268 


1.9038 


21.677 


37.393 


7.0 


49.000 


343.000 


2.6458 


1.9129 


21.991 


38.485 


7.1 


50.410 


3.57.911 


2.6646 


1.9220 


22.. 305 


39.592 


7.2 


51.840 


373.248 


2.6833 


1.9310 


22.619 


40.715 


7.3 


53.290 


389.017 


2.7019 


1.9399 


22.934 


41.854 


7.4 


54.760 


405.224 


2.7203 


1.9487 


23.248 


43.008 


7.5 


56.250 


421.875 


2.7386 


1.9574 


23.562 


44.179 


7.6 


57.760 


438.976 


2.7568 


1.9661 


23.876 


45.365 


7.7 


59.290 


456.533 


"2.7749 


1.9747 


24.190 


46.566 


7.8 


60.840 


474-552 


2.7929 


1.9832 


24.504 


47.784 


7.9 


62.410 


493.039 


2.8107 


1.9916 


24.819 


49.017 


8.0 


64.000 


512.000 


2.8284 


2.0000 


25.133 


50.266 


8.1 


65.610 


531.441 


2.8461 


2.0083 


25.447 


51.530 


8.2 


67.240 


551.468 


2.8636 


2.0165 


25.761 


52.810 


8.3 


68.890 


571.787 


2.8810 


2.0247 


26.075 


54.106 


8.4 


70.560 


592.704 


2.8983 


2.0328 


26.389 


55.418 


8.5 


72.2.50 


614.125 


2.9155 


2.0408 


26.704 


56.745 


8.6 


73.960 


636.0.56 


2.9326 


2.0488 


27.018 


58.088 


8.7 


75.690 


6.58.503 


2.9496 


2.0567 


27.332 


59.447 


8.8 


77.440 


681.473 


2.9665 


2.0646 


27.646 


60.821 


8.9 


79.210 


704.969 


2.9833 


2.0724 


27.960 


62.211 



401 













Circle 


No. 


. Square 


Cube 


Sq. 


Cube 










Diam. 






Root 


Root 


Circumf . 


Area 


9.0 


81.000 


729.000 


3.0000 


2.0'801 


28.274 


63.617 


9.1 


82.810 


753.571 


3.0166 


2.0878 


28.588 


65.039 


9.2 


84.640 


778.688 


3.0332 


2.0954 


28.903 


66.476 


9.3 


86.490 


804.357 


3.0496 


2.1029 


29.217 


67.929 


9.4 


88.380 


830.5'84 


3.0659 


2.1105 


29.531 


69.398 


9.5 


90.250 


857.375 


3.0822 


2.1179 


29.845 


70.882 


9.6 


92.160 


884.736 


3.0984 


2.1253 


30.159 


72.382 


9.7 


94.090 


912.673 


3.1145 


2.1327 


30.473 


73.898 


9.8 


96.040 


941.192 


3.1305 


2.1400 


30.788 


75.430 


9.9 


98.010 


970.299 


3.1464 


2.1472 


31.102 


76.977 


10 


100. GOO 


lOOO.OOO 


3.1623 


2.1544 


31.416 


78.. 540 


11 


121.000 


1331.000 


3.. 3166 


2.2239 


34.558 


95.033 


12 


144.000 


1728.000 


3.4641 


2.2894 


37.699 


113.097 


13 


169.000 


2197.000 


3.6056 


2.3513 


40.841 


132.732 


14 


196.000 


2744.000 


3.7417 


2.4101 


43.982 


153.938 


15 


225.000 


3375.000 


3.8730 


2.4662 


47.124 


176.715 


16 


256.00'0 


4096.000 


4.0000 


2.5198 


50.265 


201.062 


17 


289.000 


4913.000 


4.1231 


2.5713 


53.407 


226.980 


18 


324.000 


5832.000 


4.2426 


2.6207 


56.549 


254.469 


19- 


361.000 


6859.000 


4.3589 


2.6684 


59.690 


283.529 


20^ 


400.000 


8000.000 


4.4721 


2.7144 


62.832 


314.159 


21 


441.000 


9261.000 


4.5826 


2.7589 


65.793 


346.361 


22 


484.000 


10648.000 


4.6904 


2.8021 


69.115 


380.133 


23 


529.000 


12167.000 


4.7958 


2.8439 


72.257 


415.476 


24 


576.000 


13824.000 


4.8990 


2.8845 


75.398 


452.389 


25 


625.000 


1.5625. OOO 


5.000O 


2.9241 


78.540 


490.874 


26 


676.000 


17576.000 


5.0990 


2.9625 


81.681 


530.929 


27 


729.000 


19683.000 


5.1962 


3.0000 


84.823 


572.555 


28 


784.000 


21952.000 


5.2915 


3.0866 


87.965 


615.752 


29 


841.000 


24389.000 


5.3852 


3.0723 


91.106 


660.520 


30 


900.000 


27000.000 


5.4772 


3.1072 


94.248 


706.858 


31 


961.000 


29791.000 


5.5678 


3.1414 


97.389 


7.54.768 


32 


1024.000 


32768.000 


5.6569 


3.1748 


100.531 


804.248 


33 


1089.000 


35i>:37.0OO 


5.7446 


3.2075 


103.673 


855.299 


34 


1156.000 


39304.000 


5.8310 


3.2396 


106.841 


907.920 


35 


1225.000 


42875.000 


5.9161 


3.2710 


109.956 


962.113 


36 


1296.000 


46656.000 


6.0000 


3.3019 


113.097 


1017.88 


37 


1369.000 


50653.000 


6.0827 


3.3322 


116.239 


1075.21 


38 


1444.000. 


54872.000 


6.1644 


3.3620 


119.381 


1134.11 


39 


1521.000 


59319.000 


6.2450 


3.3912 


122.522 


1194.59 


40 


1600.000 


64000.000 


6.3246 


3.4200 


125.66 


1256.64 


41 


1681.000 


68921.000 


6.4031 


3.4482 


128.81 


1320.25 


42 


1764.000 


74088.000 


6.4807 


3.4760 


131.95 


1385.44 


43 


1849.000 


79507.000 


6.5574 


3.5034 


13.5.09 


1452.20 


44 


1936.000 


85184.000 


6.6333 


3.5308 


138.23 


1520.53 



402 













Circle 


No. 
Diam. 


Square 


Cube 


Sq. 
Root 


Cube 
Root 






Circumf. 


Area 


45 


2025.000 


91125.000 


6.7082 


3.. 5.569 


141.. 37 


1.590.43 


46 


2116.000 


97336.000 


6.7823 


3.. 5830 


144.51 


1661.90 


47 


2209.000 


103823.000 


6.8557 


3.6088 


147.65 


1734.94 


48 


2304.000 


110.592.000 


6.9282 


3.6342 


150.80 


1809.56 


49 


2401.000 


117649.000 


7.0000 


3.6.593 


153.94 


1885.74 


50 


2500.000 


12.5000.000 


7.0711 


3.6840 


157.08 


1963.50 


51 


2601.000 


132651.000 


7.1414 


3.7084 


160.22 


2042.82 


52 


2704.000 


140608.000 


7.2111 


3.7325 


163.36 


2123.72 


53 


2809.000 


148877.000 


7.2801 


3.7563 


166.50 


2206.18 


54 


2916.000 


157464.000 


7.3485 


3.7798 


169.65 


2290.22 


55 


3025.000 


166375.000 


7.4162 


3.8030 


172.79 


2375.83 


56 


3136.000 


175616.000 


7.4833 


3.8259 


175.93 


2463.01 


57 


3249.000 


185193.000 


7.5498 


3.8485 


179.07 


2551.76 


58 


3364.000 


19.5112.000 


7.6158 


3.8709 


182.21 


2642.08 


59 


3481.000 


205379.000 


7.6811 


3.8930 


185.35 


2733.97 


60 


3600.000 


216000.000 


7.7460 


3.9149 


188.50 


2827.43 


61 


3721.000 


226981.000 


7.8102 


3.9365 


191.64 


2922.47 


62 


3844.000 


238328.000 


7.8740 


3.9579 


194.78 


3019.07 


63 


3969.000 


250047.000 


7.9373 


3.9791 


197.92 


3117.25 


64 


4096.000 


262144.000 


8.0000 


4.0000 


201.06 


3216.99 


65 


4225.000 


274625.000 


8.0623 


4.0207 


204.20 


3318.31 


66 


4356.000 


287496.000 


8.1240 


4.0412 


207.34 


3421.19 


67 


4489.000 


300763.000 


8.1854 


4.0615 


210.49 


3525.65 


68 


4624.000 


314432.000 


8.2462 


4.0817 


213.63 


3631.68 


69 


4761.000 


328509.000 


8.3066 


4.1016 


216.77 


3739.28 


70 


4900.000 


343000.000 


8.3666 


4.1213 


219.91 


3848.45 


71 


5041.000 


357911.000 


8.4261 


4.1408 


223.05 


3959.19 


72 


5184.000 


373248.000 


8.4853 


4.1602 


226.19 


4071.50 


73 


5329.000 


389017.000 


8.. 5440 


4.1793 


229.34 


4185.39 


74 


5476.000 


405224.000 


8.6023 


4.19&3 


232.48 


4300.84 


75 


5625.000 


421875.000 


8.6603 


4.2172 


235.62 


4417.86 


76 


5776.000 


438976.000 


8.7178 


4.2358 


, 238.76 


4.536.46 


77 


5929.000 


456533.000 


8.7750 


4.2543 


241.90 


4656.63 


78 


6084.000 


474.552.000 


8.8318 


4.2727 


245.04 


4778.36 


79 


6241.000 


493039.000 


8.8882 


4.2908 


248.19 


4901.67 


80 


6400.000 


512000.000 


8.9443 


4.3089 


251.33 


.5026.55 


81 


6.561.000 


531441.000 


9.0000 


4.3267 


254.47 


5153.00 


82 


6724.000 


551368.000 


9.0554 


4.3445 


257.61 


5281.02 


83 


6889.000 


571787.000 


9.1104 


4.3621 


660.75 


5410.61 


84 


7056.000 


592704.000 


9.1652 


4.3795 


263.89 


5541.77 


85 


7225.000 


614125.000 


9.2195 


4.3968 


267.04 


5674.50 


86 


7396.000 


6360.56.000 


9.27.36 


4.4140 


270.18 


5808.80 


87 


7569.000 


658503.000 


9.3274 


4.4310 


273.32 


5944.68 


88 


7744.000 


681472.000 


9.3808 


4.4480 


276.46 


6082.12 


89 


7921.000 


704969.000 


9.4340 


4.4647 


279.60 


6221.14 













Circle 


No. 


Square 


Cube 


Sq. 


Cube 










Diam. 






Eoot 


Root 


Circumf. 


Area 


90 


8100.000 


729000.000 


9.4868 


4.4814 


282.74 


6361.73 


91 


8281.000 


753571.000 


9.5394 


4.4979 


285.88 


6503.88 


92 


8464.000 


778688.000 


9.5917 


4.5144 


289.03 


6647.61 


9'3 


8649.000 


804357.000 


9.6437 


4.5307 


292.17 


6792.91 


94 


8836.000 


830584.000 


9.69.54 


4.5468 


295.31 


6939.78 


95 


9025.000 


857375.000 


9.7468 


4.-5629 


298.45 


7088.22 


96 


9216.000 


884736.000 


9.7980 


4.5789 


301.. 59 


7238.23 


97 


9409.000 


912673.000 


9.8489 


4.5947 


304.73 


7389.81 


98 


9604.000 


941192.000 


9.8995 


4.6104 


307.88 


7542.96 


99 


9801.000 


970299.000 


9.9499 


4.6261 


311.0-2 


7697.69 


lOO 


lOOOO.OOO 


lOOOOOO.OOO 


lO.OOOO 


4.6416 


314.16 


7853.98 


105 


11025.000 


1157625.000 


10.2470 


4.7177 


329.87 


8659.01 


110 


12100.000 


1331000.000 


10.4881 


4.7914 


345.58 


9503.32 


115 


13225.000 


1520875.000 


10.7238 


4.8629 


361.28 


10386.89 


120 


14400.000 


1728000.000 


10.9545 


4.9324 


376.99 


11309.73 


125 


15625.000 


1953125.000 


11.1803 


5.OO0O 


392.70 


12271 85 


130 


16900.000 


2197000.000 


11.4018 


5.0658 


408.41 


13273.23 


135 


18225.000 


2460375. 000. 


11.6190 


5.1299 


424.12 


14313.88 


140 


19600.000 


^744000.000 


11.8322 


5.1925 


439.82 


15393.80 


145 


21025.000 


3048625.000 


12.0416 


5.2536 


455.53 


16513.00 


150 


22500.000 


3375000.000 


12.2474 


5.3133 


471.24 


17671.46 


155 


24025. OOO 


3723875.000 


12.4499 


5.3717 


486.95 


18869.19 


160 


25600.000 


4096000.000 


12.6491 


5.4288 


502.65 


20106.19 


165 


27225.000 


4492125.000 


12.8452 


5.4848 


518.36 


21882.46 


170 


28900.000 


4913000.000 


13.0384 


5.5397 


534.07 


22698.01 


175 


30625.000 


5359375.000 


13.2288 


5.5934 


549.78 


24052.82 


180 


32400.000 


5832000.000 


13.4164 


5.6462 


565.49 


25446.90 


185 


34225.000 


6331625.000 


13.6015 


5.6980 


581.19 


26880.25 


190 


36100.000 


6859000.000 


13.7840 


5.7489 


596.90 


28352.87 


195 


38025.000 


7414875.000 


13.9642 


5.7989 


612.61 


29864.77 


200 


40000.000 


8000000.000 


14.1421 


5.8480 


628.32 


31415.93 


205 


42025. 'OOO 


861.5125.000 


14.3178 


5.8964 


644.03 


33006.36 


210 


44100.000 


9261000.000 


14.4914 


5.9439 


659.73 


34636.06 


215 


46225.000 


9938375.000 


14.6629 


5.9907 


675.44 


36305.03 


220 


48400.000 


10648000.000 


14.8324 


6.0368 


691.15 


38013.27 


225 


50625.000 


11390625.000 


15.:0000 


6.0822 


706.86 


39760.78 


230 


52900.000 


12167000.000 


15.1658 


6.1269 


722.57 


41547.56 


235 


55225.000 


12977875.000' 


15.3297 


6.1710 


738.27 


43373.61 


240 


57600.000 


13824000.000 


15.4919 


6.2145 


7.53.98 


4.5238.93 


245 


00025.000 


14706125.000 


15.6525 


6.2573 


769.69 


47143.52 


250 


62500.000 


15625000.000 


15.8114 


6.2996 


785.40 


49087.39 


255 


65025.000 


16581375.000 


15.9687 


6.3413 


801.11 


51070.52 


260 


67600.000 


17576000.000 


16.1245 


6.3825 


816.81 


53092.92 


265 


70225.000 


18609625.000 


16.2788 


6.4232 


832.52 


55154.59 


270 


72900.000 


19683000.000 


16.4317 


6.4633 


848.23 


57255.53 



404 













Circle 


No. 
Diam. 


Square 


Cube 


Sq. 
Root 


Cube 
Root 






Cireumf . 


Area 


275 


75625.000 


20796875.000 


16.5831 


6.5030 


863.94 


59395.74 


280 


78400.000 


21952000.000 


16.7332 


6.5421 


879.65 


61575.22 


285 


81225.000 


23149125.000 


16.8819 


6.5808 


895.35 


63793.97 


290 


84100.000 


24389000.000 


17.0294 


6.6191 


911.06 


66061.99 


295 


87025.000 


25672375.000 


17.1756 


6.6569 


926.77 


68349.28 


300 


90000.000 


27000000.000 


17.3205 


6.6943 


942.48 


70685.83 


305 


93025.000 


28372625.000 


17.4642 


6.7313 


958.19 


73061.66 


310 


96100.000 


29791000.000 


17.6068 


6.7679 


973.89 


75476.76 


315 


99225.000 


31255875.000 


17.7482 


6.8041 


989.60 


77931.13 


320 


102400.000 


32768000.000 


17.8885 


6.8399 


1005.31 


80424.77 


325 


1(^625.000 


34328125.000 


18.0278 


6.8753 


1021.02 


82957.68 


330 


108900.000 


35937000.000 


18.1659 


6.9104 


1036.73 


85529.86 


335 


112225.000 


37595375.000 


18.3030 


6.9451 


1052.43 


88141.31 


340 


115600.000 


39.304000.000 


18.4391 


6.9795 


1068.14 


90792.03 


345 


119025.000 


41063625.000 


18.5742 


7.0136 


1083.85 


93482.02 


350 


122500.000 


42875000.000 


18.7083 


7.0473 


1099.56 


96211.28 


355 


126025.000 


44738875.000 


18.8414 


7.0807 


1115.27 


98979.80* 


360 


129600.000 


46656000.000 


18.9737 


7.1138 


1130.97 


101787.60 


365 


133225.000 


48627125.000 


19.1050 


7.1466 


1146.68 


104634.67 


370 


136900.000 


5065S0OO.00O 


19.2354 


7.1791 


1162.39 


107521.01 


375 


140625.000 


52734375.000 


19.8649 


7.2112 


1178.10 


110446.62 


380 


144400.000 


54872000.000 


19.4936 


7.2432 


1193.81 


113411.49 


385 


148225.000 


57066625.000 


19.6214 


7.2748 


1209.51 


116415.64 


390 


152100.000 


59319000.000 


19.7484 


7.3061 


1225.22 


119459.06 


395 


156025.000 


61629875.000 


19.8746 


7.3372 


1240.93 


122541.75 


400 


160000.000 


64000000.000 


20.0000 


7.3681 


1256.64 


125663.71 


405 


164025.000 


66430125.000 


20.1246 


7.3986 


1272.35 


128824.93 


410 


168100.000 


68921000.000 


20.2485 


7.4290 


1288.05 


132025.43 


415 


172225.000 


71473375.000 


20.3715 


7.4590 


1303.76 


135265.20 


420 


176400.000 


74088000.000 


20.4939 


7.4889 


1319.47 


138544.24 


425 


180625.000 


76765625.000 


20.6155 


7.5185 


1335.18 


141862.54 


430 


184900.000 


79507000.000 


20.7364 


7.5478 


1350.88 


145220.12 


435 


189225.000 


82312875.000 


20.8567 


7.5770 


1366.59 


148616.97 


440 


193600.000 


85184000.000 


20.9762 


7.6059 


1382.30 


152058.08 


445 


198025.000 


88121125.000 


21.0950 


7.6346 


1398.01 


155528.47 


450 


202500.000 


91125000.000 


21.2132 


7.6631 


1413.72 


159043.13 


455 


207025.000 


94196375.000 


21.3307 


7.6914 


1429.42 


162597.05 


460 


211600.000 


97336000.000 


21.4476 


7.7194 


1445.13 


166190.25 


465 


216225.000 


100544625.000 


21.5639 


7.7473 


1460.84 


169822.72 


470 


220900.000 


103823000.000 


21.6795 


7.7750 


1476.55 


173494.45 


475 


225625.000 


107171875.000 


21.7945 


7.8025 


1492.26 


177205.46 


480 


230400.000 


110592000.000 


21.9089 


7.8297 


1507.96 


180955.74 


485 


235225.000 


114084125.000 


22.0227 


7.&568 


1523.67 


184745.28 


490 


240100.000 


117649000.000 


22.1359 


7.8837 


1539.38 


188574.10 


495 


245025.000 


121287375.000 


22.2486 


7.9105 


1555.09 


192442.18 


500 


250000.000 


125000000.000 


22.3607 


7.9370 


1570.80 


196349.54 



40c 



TABLE 2. 
Trigonometric Functions. 



Angle, 


Sine 


Tangent 




Angle, 


Sine 


Tangent 




degrees 








degrees 








0.0 


o.ooooo 


0.00000 


90.0 


47.5 


0.73728 


1.0913 


42.5 


2.5 


0.04362 


0.04362 


87.5 


50.0 


0.76604 


1.1917 


40.0 


5.0 


0.08716 


0.08749 


85.0 


52.5 


0.79335 


1.3032 


37.5 


7.5 


0.13053 


0.13m5 


82.5 


55.0 


0.81915 


1.4281 


35.0 


10.0 


0.17365 


0.17633 


80.0 


57.5 


0.84339 


1.5697 


32.5 


12.5 


0.21644 


0.22169 


77.5 


60.0 


0.86603 


1.7321 


30.0 


15.0 


0.25882 


0.26795 


75.0 


62.5 


0.88701 


1.9210 


27.5 


17.5 


0.30071 


0.31530 


72.5 


65.0 


0.90631 


2.1445 


25.0 


20.0 


0.34202 


0.36397 


70.0 


67.5 


0.92388 


2.4142 


22.5 


22.5 


0.88263 


0.41421 


67.5 


70.0 


0.93969 


2.7474 


20.0 


25.0 


0.42262 


0.46631 


65.0 


72.5 


0.95372 


3.1716 


17.5 


27.5 


0.46175 


0.52057 


62.5 


75.0 


0.96593 


3.7321 


15.0 


30.0 


0.50000 


0.57735 


60.0 


77.5 


0.97630 


4.5107 


12.5 


32.5 


0.53730 


0.63707 


57.5 


80.0 


0.98481 


5.6713 


10.0 


35.0 


0.57358 


0.70021 


56.0 


82.5 


0.99144 


7.5958 


7.5 


37.5 


0.60876 


0.76733 


52.5 


85.0 


0.99619 


11.430 


5.0 


40.0 


0.64279 


0.83910 


50.0 


87.0 


0.99863 


19.0S1 


3.0 


42.5 


0.67559 


0.91633 


47.5 


88.5 


0.99966 


38.188 


1.5 


45.0 


0.70711 


1.0000 


45.0 


9O.0 


l.OOOO 


Infinite 


0.0 




Cosine 


Cotan- 


Angle, 




Cosine 


Cotan- 


Angle, 






gent 


degrees 






gent 


degrees 



TABLE 3. 
Equivalents of Compound Units. 



1 lb. per sq. in. 



1 oz. per sq. in. 



1 in. of water at 62° F. 



1 in. of water at 



1 in. of mercury at 62° F. 



1 ft. of air at 32° F. 



' 27.71 in. of water at 62° F. 

2.0355 in. of mercxn-y at 32° F. 

2.0416 in. of mercury at 62° F. 

2.309O ft. of water at 62° F. 
.1784. ft. of air at 32° F. 



^ Jo. 1276 in. of 
1^1.732 in. of 



f mercury at 62° F. 
water at 62° F. 



,196 
.0736 



lb. or .5574 oz. per s. in. 

lbs. per sq. ft. 

in. of mercury at 62° F. 



J 5.2021 lbs. per sq. ft. 
1^0.036125 lb. per sq. in. 



■{,■ 



491 lb. or 7.86 oz. per sq. in. 
132 ft. of water at 62° F. 
13.58 in. of water at 62° F. 



0005606 lb. per sq. in. 
015534 in. of water at 6%° F. 



40(3^ 



TABLE 4. 
Properties of Saturated Steam. =• 



Abs. 


Temp., 


Sp. vol.. 


Density, 


Heat 


Latent 


Heat 


pres . , 


deg. 


cu. ft. 


lb. per 


of the 


heat of 


content 


lb., 


fahr., 


per lb., 


cu. ft., 


liquid. 


evap.. 


of steam. 


P 


t 


v" 


1/y" 


r 


r 


i" 


1 


101.83 


333.0 


0.00300 


69.8 


1034.6 


1104.4 


2 


126.15 


173.5 


0.00576 


94.0 


1021.0 


1115.0 


3 


141.52 


118.5 


0.00845 


109.4 


1012.3 


1121.6 


4 


153.01 


90.5 


0.01107 


120.9 


1005.7 


1126.5 


5 


162.28 


73.33 


0.01364 


130.1 


1000.3 


1130.5 


6 


170.06 


61.89 


0.01616 


137.9 


995.8 


1133.7 


7 


176.85 


53.56 


0.01867 


144.7 


991.8 


1136.5 


8 


182.86 


47.27 


0.02115 


150.8 


988.2 


1139.0 


9 


188.27 


42.36 


0.02361 


156.2 


985.0 


1141.1 


10 


193.22 


38.38 


0.02606 


161.1 


982.0 


1143.1 


11 


197.75 


35.10 


0.02849 


165.7 


979.2 


1144.9 


12 


201.96 


32.36 


0.08O9O 


169.9 


976.6 


1146.5 


13 


205.87 


30.03 


0.03330 


173.8 


974.2 


1148.0 


14 


209.55 


28.02 


0.03569 


177.5 


971.9 


1149.4 


14.7 


212.00 


26.79 


0.03732' 


180.0 


970.4 


11.50.4 


15 


213.0 


26.27 


0.0:3806 


181.0 


969.7 


11.50.7 


16 


216.3 


24.79 


0.04042 


184.4 


967.6 


11.52.0 


17 


219.4 


23.38 


0.04277 


187.5 


965.6 


1153.1 


18 


222 . 4 


22.16 


0.04512 


190.5 


963.7 


1154.2 


19 


225 ".2 


21.07 


0.04746 


193.4 


961.8 


1155.2 


20 


228.0 


20.08 


0.04980 


196.1 


960.0 


1156.2 


21 


230.6 


19.18 


0.05213 


198.8 


958.3 


11.57.1 


221 


233.1 


18.37 


0.05445 


201.3 


956.7 


1158.0 


23 


235.5 


17.62 


0.05676 


203.8 


9.55.1 


1158.8 


24 


237.8 


16.93 


0.05907 


206.1 


953.5 


1159.6 


25 


240.1 


16.30 


0.0614 


208.4 


952.0 


1160.4 


26 


242.2 


15.72 


0.0636 


210.6 


950.6 


1161.2 


27 


244.4 


15.18 


0.06.59 


212.7 


949.2 


1161.9 


28 


246.4 


14.67 


0.0682 


214.8 


947.8 


1162.6 


29 


248.4 ■ 


14.19 


0.0705 


216.8 


946.4 


1163.2 


30 


250.3 


13.74 


0.0728 


218.8 


945.1 


1163.9 


31 


252.2 


13.32 


0.0751 


220.7 


943.8 


1164.5 


32 


254.1 


12.93 


0.0773 


222.6 


942.5 


1165.1 


33 


255.8 


12.57 


0.0795 


224.4 


941.3 


1165.7 


34 


257.6 


12.22 


0.0818 


226.2 


940.1 


1166.3 


3.5 


259.3 


11.89 


0.0841 


227.9 


938.9 


1166.8 


36 


261.0 


11.58 


0.0863 


229.6 


937.7 


1167.3 


37 


262.6 


11.29 


.0.0886 


231.3 


936.6 


1167.8 


38 


264.2 


11.01 


0.0908 


232.9 


935.5 


1168.4 


39 


265.8 


10.74 


0.0931 


234.5 


934.4 


1168.9 


40 


267.3 


10.49 


0.0953 


236.1 


933.3 


1169.4 


41 


268.7 


10.25 


0.0976 


237.6 


9.32.2 


1169.8 


42 


270.2 


10.02 


0.0998 


239.1 


931.2 


1170.3 


43 


271.7 


9.80 


0.1020 


240.5 


930.2 


1170.7 


44 


273.1 


9.59 


0.1043 


242.0 


929.2 


1171.2 


4.5 


274.5 


9.39 


0.1065 


243.4 


928.2 


1171.6 


46 


275.8 


9.20 


0.1087 


244.8 


927.2 


1172.0 


47 


277.2 


9.02 


0.1109 


246.1 


926.3 


1172.4 


48 


278.5 


8.84 


0.1131 


247.5 


925.3 


1172.8 


49 


279.8 


8.67 


0.11.53 


248.8 


924.4 


1173.2 



M^rks and Davis, Handbook. 



Abs. 


Temp., 


Sp. vol., 


Density, 


Heat 


Latent 


Heat 


pres., 


deg. 


cu. ft. 


lb. per 


of the 


heat of 


content 


lb., 


fahr., 


per lb . , 


cu. ft.. 


liquid. 


evap . , 


of steam. 


P 


* 


V" 


1/v" 


*' 


r 


i" 


50 


281.0 


8.51 


0.1175 


250.1 


923.5 


1173.6 


■ 51 


282.3 


8.35 


0.1197 


251.4 


922.6 


1174.0 


52 


283.5 


8.20 


0.1219 


252.6 


921.7 


1174.3 


53 


284.7 


8.05 


0.1241 


253.9 


920.8 


1174.7 


54 


285.9 


7.91 


0.1263 


255.1 


919.9 


1175.0 


55 


287.1 


7.78 


0.1285 


2.56.3 


919.0 


1175.4 


56 


288.2 


7.65 


0.1307 


257.5 


918.2 


1175.7 


57 


289.4 


7.52 


0.1329 


258.7 


917.4 


1176.0 


58 


290.5 


7.40 


0.1350 


259.8 


916.5 


1176.4 


59 


291.6 


7.28 


0.1372 


261.0 


915.7 


1176.7 


60 


292.7 


7.17 


0.1394 


262.1 


914.9 


1177.0 


61 


293.8 


7.06 


0.1416 


263.2 


914.1 


1177.3 


62 


294.9 


0.95 


0.1438 


264.3 


913.3 


1177.6 


63 


295.9 


6.85 


0.1460 


265.4 


912.5 


1177.9 


64 


297.0 


6.75 


0.14^ 


266.4 


911.8 


1178.2 


65 


298.0 


6.65 


0.1.503 


267.5 


911.0 


1178.5 


66 


299.0 


6.56 


0.1.525 


268.5 


910.2 


1178.8 


67 


300.0 


6.47 


0.1547 


269.6 


909.5 


1179.0 


OS 


301.0 


6.38 


0.1569 


270.6 


908.7 


1179.3 


69 


■ 302.0 


6.29 


0.1590 


271.6 


908.0 


1179.6 


70 


302.9 


6.20 


0.1612 


272.6 


907.2 


1179.8 


71 


303.9 


6.12 


0.1634 


273.6 


906.5 


1180.1 


72 


304.8 


6.04 


0.1656 


274.5 


905.8 


1180.4 


73 


305.8 


5.96 


0.1678 


275.5 


905.1 


1180.6 


74 


306.7 


5.89 


0.1699 


276.5 


904.4 


1180.9 


75 


307.6 


5.81 


0.1721 


277.4 


903.7 


1181.1 


76 


308.5 


5.74 


0.1743 


278.3 


903.0 


1181.4 


77 


309.4 


5.67 


0.1764 


279.3 


902.3 


1181.6 


78 


310.3 


5.60 


0.1786 


280.2 


901.7 


1181.8 


79 


311.2 


5.54 


0.1808 


281.1 


901.0 


1182.1 


80 


312.0 


5.47 


0.1829 


282.0 


900.3 


1182.3 


81 


312.9 


5.41 


0.1851 


282.9 


899.7 


1182.5 


82 


313.8 


5.34 


0.1873 


283.8 


899.0 


1182.8 


83 


314.6 


5.28 


0.1894 


284.6 


898.4 


1183.0 


84 


315.4 


5.22 


0.1915 


285.5 


897.7 


1183.2 


85 


316.3 


=.16 


0.1937 


286.3 


897.1 


1183.4 


86 


317.1 


5.10 


0.1959 


287.2 


896.4 


1183.6 


87 


317.9 


5.05 


0.1980 


288.0 


895.8 


1183.8 


88 


318.7 


5.00 


O.20O1 


288.9 


895.2 


1184.0 


89 


319.5 


4.94 


0.2023 


289.7 


894.6 


1184.2 


90 


320.3 


4.89 


0.2044 


290.5 


893.9 


1184.4 


91 


321.1 


4.84 


0.2065 


291.3 


893.3 


1184.6 


92 


321.8 


4.79 


0.2087 


292.1 


892.7 


1184.8 


93 


322.6 


4.74 


0.2109 


292.9 


892.1 


1185.0 


94 


323.4 


4.69 


0.2130 


293.7 


891.5 


1185.2 


95 


324.1 


4.65 


0.2151 


294.5 


890.9 


1185.4 


96 


324.9 


4.60 


0.2172 


295.3 


890.3 


1185.6 


97 


325.6 


4.56 


0.2193 


296.1 


889.7 


11&5.8 


98 


326.4 


4.51 


0.2215 


296.8 


889.2 


1186.0 


99 


327.1 


4.47 


0.2237 


297.6 


888.6 


1186.2 



Abs. 


Temp., 


Sp. vol., 


Density, 


Heat 


Latent 


Heat 


pres., 


deg-. 


cu. ft. 


lb. per 


of the 


heat of 


content 


lb., 


fahr., 


per lb., 


cu. ft.. 


liquid, 


evap.. 


of steam. 


P 


t 


V" 


1/v" 


i' 


r 


i" 


100 


327.8 


4.429 


0.2258 


298.3 


888.0 


1186.3 


102 


329.3 


4.347 


0.2300 


299.8 


886.9 


1186.7 


104 


330.7 


4.268 


0.2343 


301.3 


885.8 


1187.0 


106 


3^.0 


4.192 


0.2386 


302.7 


884.7 


1187.4 


108 


333.4 


4.118 


0.2429 


304.1 


883.6 


1187.7 


110 


334.8 


4.047 


0.2472 


305.5 


882.5 


1188.0 


112 


336.1 


3.978 


0.2514 


306.9 


881.4 


1188.4 


114 


337.4 


3.912 


0.2556 


308.3 


880.4 


1188.7 


116 


338.7 


3.848 


0.2599 


309.6 


879.3 


1189.0 


118 


340.0 


3.786 


0.2641 


311.0 


878.3 


1189.3 


120 


341.3 


3.726 


0.2683 


312.3 


877.2 


1189.6 


122 


342.5 


3.668 


0.2726 


313.6 


876.2 


1189.8 


124 


343.8 


3.611 


0.2769 


314.9 


875.2 


1190.1 


126 


345.0 


3.556 


0.2812 


316.2 


874.2 


1190.4 


128 


346.2 


3.504 


0.2854 


317.4 


873.3 


1190.7 


130 


347.4 


3.452 


0.2897 


318.6 


872.3 


1191.0 


132 


348.5 


3.402 


0.2939 


319.9 


871.3 


1191.2 


134 


349.7 


3.354 


0.2981 


321.1 


870.4 


1191.5 


136 


350.8 


3.308 


0.3023 


322.3 


869.4 


1191.7 


138 


352.0 


3.263 


0.3065 


323.4 


868.5 


1192.0 


140 


353.1 


3.219 


0.3107 


324.6 


867.6 


1192.2 


142 


854.2 


3.175 


0.3150 


325.8 


866.7 


1192.5 


144 


355.3 


3.133 


0.3192 


326.9 


865.8 


1192.7 


146 


356. S 


3.0O2 


0.3234 


328.0 


864.9 


1192.9 


148 


357.4 


3.052 


0.3276 


329.1 


864.0 


1193.2 


150 


358.5 


3.012 


0.3320 


.330.2 


863.2 


1193.4 


152 


359.5 


2.974 


0.3362 


331.4 


862.3 


1193.6 


154 


360.5 


2.938 


0.3404 


332.4 


861.4 


1193.8 


156 


361.6 


2.902 


0.3446 


333.5 


860.6 


1194.1 


158 


362.6 


2.868 


0.3488 


334.6 


859.7 


1194.3 


160 


363.6 


2.834 


0.3529 


335.6 


858.8 


1194.5 


162 


364.6 


2.801 


0.3570 


336.7 


858.0 


1194.7 


164 


365.6 


2.769 


0.3612 


337.7 


8.57.2 


1194.9 


166 


366.5 


2.737 


0.3654 


338.7 


856.4 


1195.1 


168 


367.5 


2.706 


0.3696 


339.7 


855.5 


1195.3 


170 


368.5 


2.675 


0.3738 


340.7 


854.7 


1195.4 


172 


369.4 


2.645 


0.3780 


341.7 


853.9 


1195.6 


174 


370.4 


2.616 


0.3822 


342.7 


853.1 


1195.8 


176 


371.3 


2.588 


0.3864 


343.7 


852.3 


1196.0 


178 


372.2 


2.560 


0.3906 


344.7 


851.5 


1196.2 


180 


373.1 


2.533 


0.3948 


345.6 


850.8 


1196.4 


182 


374.0 


2.507 


0.3989 


346.6 


850.0 


1196.6 


1^ 


374.9 


2.481 


0.4031 


347.6 


849.2 


1196.8 


186 


375.8 


2.455 


0.4073 


348.5 


848.4 


1196.9 


188 


376.7 


2.430 


0.4115 


349.4 


847.7 


1197.1 


190 


377.6 


2.406 


0.4157 


350.4 


846.9 


1197.3 


192 


378.5 


2.381 


0.4199 


351.3 


846.1 


1197.4 


194 


379.3 


2.358 


0.4241 


352.2 - 


845.4 


1197.6 


196 


380.2 


2.335 


0.4283 


353.1 


844.7 


1197.8 


198 


381.0 


2.312 


0.4325 


354.0 


843.9 


1197.9 



Abs. 


Temp . , 


Sp. vol., 


Density, 


Heat 


Latent 


Heat 


pres., 


deg. 


cu. ft. 


lb. per 


of the 


heat of 


content 


lb., 


fahr., 


per lb., 


cu. ft., 


liquid, 


evap.. 


of steam. 


P 


t 


v" 


1/v" 


*' 


r 


i" 


200- 


381.9 


2.290 


0.4.37 


354.9 


843.2 


1198.1 


205 


384.0 


2.237 


0.447 


357.1 


841.4 


1198.5 


210 


386.0 


2.187 


0.457 


359.2 


839.6 


1198.8 


215 


388.0 


2.138 


0.468 


361.4 


837.9 


1199.2 


220 


389.9 


2.091 


0.478 


363.4 


836.2 


1199.6 


225 


391.9 


2.046 


0.489 


365.5 


834.4 


1199.9 


230 


393.8 


2.004 


0.499 


367.5 


832.8 


120O.2 


235 


395.6 


1.964 


0.50O 


369.4 


831.1 


1200.6 


240 


397.4 


1.924 


0.520 


371.4 


829.5 


1200.9 


245 


3J)0.3 


1.887 


0..580 


373.3 


827.9 


1201.2 


250 


401.1 


1.850 


0.541 


375.2 


826.3 


1201.5 


260 


404.5 


1.782 


0.561 


378.9 


823.1 


1202.1 


270 


407.9 


1.718 


0.582 


382.5 


820.1 


1202.6 


280 


411.2 


1.6.58 


0.603 


386.0 


817.1 


1203.1 


290 


414.4 


1.602 


0.624 


389.4 


814.2 


1203. e 


30O 


417.5 


1.551 


0.645 


392.7 


811.3 


1204.1 


350 


431.9 


1.334 


0.750 


408.2 


797.8 


1206.1 


400 


444.8 


1.17 


0.86 


422.0 


786.0 


1208.0 


450 


456.5 


1.04 


0.96 


435.0 


774.0 


1209.0 


50O 


467.3 


0.93 


1.08 


448.0 


762.0 


1210.0 


660 


486.6 


0.76 


1.32 


469.0 


741.0 


1210.0 



TABLE 5. 



Naperian LiOgaritliiiis. 

2.7182818 Log- e = 0.4342945 



M. 



1.0 


0.0000 


4.1 


1.4110 


7.2 


1.9741 


1.1 


0.0953 


4.2 


1.4351 


7.3 


1.9879 


1.2 


0.1823 


4.3 


1.4586 


7.4 


2.0(J15 


1.3 


0.2624 


4.4 


1.4816 


7.5 


2.0149 


1.4 


0.3365 


4.5 


1.5041 


7.6 


2.0281 


1.5 


0.4055 


4.6 


1..5261 


7.7 


2.0412 


1.6 


0.4700 


4.7 


1..5476 


7.8 


2.0541 


1.7 


0.5306 


4.8 


1.5686 


7.9 


2.0669 


1.8 


0.5878 


4.9 


1.5892 


8.0 


2.0794 


1.9 


0.6419 


5.0 


1.6094 


8.1 


2.0919 


2.0 


0.6931 


5.1 


1.6292 


8.2 


2.1041 


2.1 


0.7419 


5.2 


1.6487 


8.3 


2.1163 


2.2 


0.7885 


5.3 


1.6677 


8.4 


2.1282 


2.3 


0.8329 


5.4 


1.6864 


8.5 


2.1401 


2.4 


0.8755 


5.5 


1.7047 


8.6 


2.1518 


2.5 


0.9163 


5.6 


1.7228 


8.7 


3.1633 


2.6 


0.9555 


5.7 


1.7405 


8.8 


2.1748 


2.7 


0.9933 


5.8 


1.7.579 


8.9 


2.1861 


2.8 


1.0296 


5.9 


1.7750 


9.0 


2.1972 


2.9 


1.0647 


6.0 


1.7918 


9.1 


2.2083 


3.0 


1.0986 


6.1 


1.8083 


. 9.2 


2.2192 


3.1 


1.1312 


6.2 


1.8245 


9.3 


2.2300 


3.2 


1.1632 


6.3 


1.8405 


9.4 


2.2407 


3.3 


1.1939 


6.4 


1.8563 


9.5 


2.2513 


3.4 


1.2238 


6.5 


1.8718 


9.6 


2.2618 


3.5 


1.2.528 


6.6 


1.8871 


9.7 


2.2721 


3.6 


1.2809 


6.7 


1.9021 


9.8 


2.2824 


3.7 


1.3083 


6.8 


1.9169 


9.9 


2.2925 


3.8 


1.3350 


6.9 


1.9315 


10.0 


2.3026 


3.9 


1.3610 


7.0 


1.94.59 






4.0 


1.3863 


7.1 


1.9601 







TABLE 6. 
Water Conversion Factors. ^^ 



U. S. gallons 


X 


8.33 


= pounds. 


U. S. gallons 


X 


0.13368 


= cubic feet. 


U. S. gallons 


X 


231.00000 


= cubic inches. 


U. S. gallons 


X 


3.78 


= liters. 


Cubic inches of water (39.1°) 


X 


0.036024 


= pounds. 


Cubic inches of water (39.1°) 


X 


0.004329 


= U. S. gallons. 


Cubic inches of water (39.1°) 


X 


0.576384 


= ounces. 


Cubic feet of water (.89.1°) 


X 


62.425 


= pounds. 


Cubic feet of water (39.1°) 


X 


7.48 


= U. S. gallons. 


Cubic feet of water (39.1") 


X 


0.028 


= tons. 


Pounds of water 


X 


27.72 


= cubic inches. 


Pounds of water 


X 


0.01602 


= cubic feet. 


Pounds of water 


X 


0.12 


= U. S. gallons. 



American Machinist Hand Book. 



411 



TABLE 7. 
Volume and Weisht of Dry Air at Different Teniiieratures.* 

Under a constant atmospheric pressure of 29.92 inches of 
mercury, the volume at 32° F. being- 1. 



Temp. 


Volume 


Weight 


Temp. 


Volume 


Weight 


deg. F. 




per cu. ft. 


deg. F. 




per eu. ft. 





.935 


.0864 


500 


1.954 


.0413 


12 


.960 


.0842 


552 


2.056 


.0385 


22 


.980 


.0824 


600 


2.150 


.0.376 


32 


l.OOO 


.0807 


650 


2.260 


.03.57 


42 


1.020 


.0791 


700 


2.362 


.0338 


52 


1.041 


.0776 


750 


2.465 


.0328 


62 


1.061 


.0761 


800 


2.566 


.0315 


72 


1.082 


.0747 


850 


2.668 


.0303 


82 


1.102 


.0733 


90O 


2.770 


.0292 


92 


1.122 


.0720 


950 


2.871 


.0281 


102 


1.143 


.0707 


1000 


2.974 


.0268 


112 


1.163 


.0694 


1100 


3.177 


.0254 


122 


1.184 


.0682 


1200 


3.381 


.0239 


132 


1.204 


.0671 


1300 


3.584 


.0225 


142 


1.224 


.0659 


140O 


3.788 


.0213 


152 


1.245 


.0649 


1500 


3.993 


.0202 


162 


1.265 


.0638 


1600 


4.196 


.0192 


172 


1.285 


.0628 


1700 


4.402 


.0183 


182 


1.306 


.0618 


180O 


4.605 


.0175 


192 


1.326 


.0609 


1900 


4.808 


.0168 


202 


1.347 


.0600 


2000 


5.012 


.0161 


212 


1.367 


.0591 


210O 


5.217 


.0155 


230 


1.404 


.0575 


2200 


5.420 


.0149 


250 


1.444 


.0559 


2300 


5.625 


.0142 


275 


1.495 


.0540 


24O0 


5.827 


.0138 


300 


1.546 


.0.522 


250O 


6.032 


.0183 


325 


1.597 


.0506 


260O 


6.236 


.0130 


350 


1.648 


.0490 


2700 


6.440 


.0125 


375 


1.689 


.0477 


2800 


6.644 


.0121 


40O 


1.750 


.0461 


2900 


6.847 


.0118 


450 


1.852 


.0436 


3000 


7.051 


.0114 



TABLE 8. 

Temperature of the Boiling' Point at Different Heights of the 

Mercury Column.f 





29.92 
212 


28.75 
210 


27.62 

208 


26.52 
206 


25.46 
204 


24.44 

202 


23.45 


Temp. F. 


200 


Inches 

Temp. F. 


22.50 
198 


21.58 
196 


20.68 
194 


19.83 
192 


19.00 
190 


18.20 
188 


17.42 
186 



* Suplee's M. E. Reference Book. 
t Smithsonian Tables. 



TABLE 9. 

AV'eight of Pure AVater per Cubic Foot at Various 

Temperatures.* 



Temp. 


Weight 


B. t. u. 


Temp . 


Weight 


B. t. n. 


deg. 


lbs. per 


per pound 


deg. 


lbs. per 


per pound 


F. 


eu. ft. 


above 82 


F. 


cu. ft. 


above 32 


32 


62.42 


0.00 


77 


62.26 


45.04 


33 


62.42 


1.01 


78 


62.25 


46.04 


34 


62.42 


2.02 


79 


62.24 


47.04 


35 


62.42 


3.02 


80 


62.23 


48.03 


36 


62.42 


4.03 


81 


62.22 


49.03 


37 


62.42 


5.04 


82 


62.21 


50.03 


38 


62.42 


6.04 


S3 


62.20 


51.02 


39 


62.42 


7.05 


84 


62.19 


52.02 


40 


62.42 


8.05 


85 


62.18 


53.02 


41 


62.42 


9.05 


86 


62.17 


54.01 


42 


62.42 


10.00 


87 


62.16 


55.01 


43 


62.42 


11.06 


88 


62.15 


56.01 


44 


62.42 


12.06 


89 


62.14 


57.00 


4^ 


62.42 


13.07 


90 


62.13 


58.00 


46 


62.42 


14.07 


91 


62.12 


59.00 


47 


62.42 


15.07 


92 


62.11 


60.00 


48 


62.41 


16.07 


93 


62.10 


60.99 


49 


62.41 


17.08 


94 


62.09 


61.99 


50 


62.41 


18.08 


95 


62,08 


62.99 


51 


62.41 


19.08 


m 


62.07 


63.98 


52 


62.40 


20.08 


97 


62.06 


64.98 


53 


62.40 


21.08 


98 


62.05 


65.98 


54 


62.40 


22.08 


99 


62.03 


66.97 


55 


62.39 


23.08 


100 


62.02 


67.97 


56 


62.39 


24.08 


101 


62.01 


68.97 


57 


62.39 


25.08 


102 


62.00 


69.96 


58 


62.38 


26.08 


103 


61.99 


70.96 


59 


62.88 


27.08 


104 


61.97 


71.96 


60 


62.. 37 


28.08 


105 


61.96 


72.95 


61 


62.37 


29.08 


108 


61.95 


73.95 


62 


62.36 


30.08 


107 


61.93 


. 74.95 


as 


62.. 36 


.31.07 


108 


61.92 


75.95 


64 


62.35 


32.07 


109 


61.91 


76.94 


65 


62.34 


.33.07 


110 


61.89 


77.94 


m 


62.34 


34.tfr 


111 


61.88 


78.94 


67 


62.33 


.3.5.07 


112 


■ 61.86 


79.93 


68 


62.33 


36.07 


113 


61.85 


80.93 




62.32 


87.06 


114 


61.83 


81.93 


70 


62.31 


38.06 


115 


61.82 


82.92 


71 


62.31 


39.06 


116 


61.80 


83.92 


72 


62.30 


40.05 


117 


61.78 


84.92 


73 


62.29 


41.05 


118 


61.77 


85.92 


74 


62.28 


42.05 


119 


61.75 


86.91 


75 


62.28 


43.05 


120 


61.74 


87.91 


76 


62.27 


44.04 


121 


61.72 


88.91 



Kent's M. 



E. Pocket-Book. 8th Edition. 
413 



Temp. 


Weight 


B. t. u. 


Temp. 


Weight 


B. t. u. 


deg-. 


lbs. per 


per pound 


deg. 


lbs. per 


per pound 


E. 


cu. ft. 


above 32 


P. 


cu. ft. 


above 32 


122 


61.70 


89.91 


167 


60.83 


134.86 


123 


61.68 


90.90 


168 


60.81 


135.86 


124 


61.67 


91.90 


169 


60.79 


136.86 


125 


61.65 


92.90 


170 


60.77 


137.87 


126 


61.63 


93.90 


171 


60.75 


1.38.87 


127 


61.61 


94.89 


172 


60.73 


139.87 


128 


61.60 


95.89' 


173 


60.70 


140.87 


129 


61.58 


96.89 


174 


60.68 


141.87 


130 


61.56 


97.80 


175 


60.66 


142.87 


131 


61.54 


98.89 


176 


60.64 


143.87 


132 


61.52 


99.88 


177 


60.62 


144.88 


133 


61.51 


100.88 


178 


. 60.59 


145.88 


134 


61.49 


101.88 


179 


60.57 


146.88 


135 


61.47 


102.88 


180 


60.55 


147.88 


136 


61.45 


103.88 - 


181 


60.53 


148.83 


137 


61.43 


104.87 


182 


60.50 


149.89 


138 


61.41 


105.87 


183 


60.48 


150.89 


139 


61.39 


106.87 


184 


60.46 


151.89 


140 


61.37 


107.87 


185 


60.44 


152.89 


141 


61.36 


108.87 


186 


60.41 


153.89 


142 


61.34 


109.87 


187 


60.39 


154.90 


143 


61.32 


110.87 


188 


60.37 


155.90 


144 


61.30 


111.87 


180 


60.34 


156.90 


145 


61.28 


112.86 


190 


60.32 


157.91 


146 


61.26 


113.86 


191 


60.29 


158.91 


147 


61.24 


114.86 


192 


60.27 


1.59.91 


148 


61.22 


115.86 


193 


60.25 


160.91 


149 


61.20 


116.86 


194 


60.22 


161.92 


150 


61.18 


117.86 


195 


60.20 


162.92 


151 


61.16 


118.86 


196 


60.17 


163.92 


152 


61.14 


119.86 


197 


60.15 


164.93 


153 


61.12 


120.86 


198 


60.12 


165.93 


154 


61.10 


121.86 


199 


60.10 


166.94 


155 


61.08 


122.86 


20O 


60.07 


167.94 


156 


61.06 


123.86 


201 


60.05 


168.94 


157 


61.04 


124.86 


202 


60.02 


169.95 


158 


61.02 


125.86 


203 


60.00 


170.95 


159 


61.00 


126.86 


204 


59.97 


171.96 


160 


60.98 


127.86 


205 


59.95 


172.96 


161 


60.96 


128.86 


206 


59.92 


173.97 


162 


60.94 


129.86 


207 


59.89 


174.97 


163 


60.92 


130.86 


208 


59.87 


175.98 


164 


60.90 


131.86 


209 


59.84 


176.98 


165 


60.87 


132.86 


210 


59.82 


177.99 ' 


166 


60.85 


133.86 


211 


59.79 


178.99 








212 


59.76 


180. 



414 



TABLE 10. 
Boiling Point of "Water at Different Heights of Vacuum. 





Height of 




Height of 


Temp. 


mercury m 


Temp. 


mercury m 


F. 


vacuum tube 


F. 


vacuum tube 




in inches 




in inches 


212.0 


0.00 


175.8 


16.00 


210.3 


l.OO 


172.6 


17.00 


208.. 5 


2.00 


169.0 


18.00 


206.8 


3.0O 


165.3 


19.00 


204.8 


4.00 


161.2 


20.00 


202.9 


5.00 


156.7 


21.00 


200.9 


6.00 


151.9 


22.00 


199.0 


7.0O 


146.5 


23.00 


196.7 


8.00 


140.3 


24.00 


194.5 


9.00 


133.3 


25.00 


192.2 


10. OO 


124.9 


26.00 


189.7 


11. OO 


114.4 


27.00 


187.3 


12.00 


108.4 


28.00 


184.6 


13.00 


102.0 


29.00 


181.3 


14.00 


98.0 


29.92 


178.9 


15.00 







TABLE 11. 

Weight of Water with Air per Cuhic Foot at Different 

Temperatures and at Saturation. 



6, 




1 


0) 03 


a 
S 




ft 

s 


is 

^5i 


6. 

1 


is 

•5 03 


ft 

s 


is 


—20 


0.166 


2 


0.529 


24 


1.483 


46 


3.539 


68 


7.480 


90 


14.790 


—19 


0.174 


3 


0..5.54 


25 


1..5.51 


47 


3.667 


69 


7.726 


91 


15.234 


—18 


0.184 


4 


0.582 


26 


1.623 


48 


3.80O 


70 


7.980 


92 


15.689 


—17 


0.196 


5 


0.610 


27 


1.697 


49 


3.936 


71 


8.240 


93 


16.155 


—16 


0.207 


6 


0.639 


28 


1.773 


50 


4.076 


72 


8.508 


94 


16.634 


—15 


0.218 


7 


0.671 


29 


1.853 


51 


4.222 


73 


8.782 


95 


17.124 


—14 


0.231 


8 


0.704 


30 


1.935 


52 


4.372 


74 


• 9.066 


96 


17.626 


—13 


0.243 


9 


0.739 


31 


2.022 


53 


4.. 526 


75 


9.356 


97 


18.142 


—12 


0.2.57 


10 


0.776 


32 


2.113 


54 


4.685 


76 


9.655 


98 


18.671 


—11 


0.270 


11 


0.810 


33 


2.194 


55 


4.849 


77 


9.962 


99 


19.212 


—10 


0.285 


12 


0.856 


34 


2.279 


56 


5.016 


78 


10.277 


10<} 


19.766 


— 9 


0.300 


13 


0.898 


35 


2.366 


57 


5.191 


79 


10.601 


101 


20.335 


— 8 


0.316 


14 


0.941 


36 


2.457 


58 


5.370 


80 


10.9.34 


102 


21.017 




0.332 


15 


0.986 


37 


2.550 


59 


5.555 


81 


11.275 


103 


21.514 


— 6 


0.350 


16 


1.032 


38 


2.646 


60 


5.745 


82 


11.626 


104 


22.125 


— 5 


0.370 


17 


1.080 


39 


2.746 


61 


5.941 


83 


11.987 


105 


22.750 


— 4 


0.389 


18 


1.128 


40 


2.849 


62 


6.142 


84 


12.3.56 


106 


23.392 


— 3 


0.411 


19 


1.181 


41 


2.955 ' 


63 


6.349 


85 


12.736 


107 


24.048 


— 2 


0.434 


20 


1.235 


42 


3.064 


64 


6.563 


86 


13.127 • 


108 


24.720 


— 1 


0.457 


21 


1.294 


43 


3.177 


65 


6.782 


87 


13.526 


109 


25.408 





0.481 


22 


1.355 


44 


3.294 


66 


7.009^ 


88 


13.937 


110 


26.112 


1 


0.505 


23 


1.418 


45 


3.414 


67 


7.241 


89 


14.. 359 







415 



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s 


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^S^8S5^^gggfeS8SSSSg§ 1 


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SI 




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SI 




si^^ 


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a. j 


t- 


S8 


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4;^sg8gssg8ii^f2^^gg^^ 


Ci 


CO J 

'^ 1 


^ 


s^ 


-* 


g;SSS^8§gFi^tti2gg^g^eg 1 


00 


«0 1:- lA r^ 
fM CO 'i* « 


ggggggeSi5gi:ggg88S55S 1 


J^- 


^ 1^ 


i^g? 


g 


coco 


gg^^^fcx^gSS^S^^iSS 1 


«o 


lo 1 


^S8 


g 


feg|2^f:ggi853g8S3aS^^8^ife 1 


LC 










^ 1 

CO 1 


^gg 


i>! 


^gg85SS^^^S^fefeSg8S^^8 1 


-* 


fe|2^g 


gsg 


^Sgfefeg§§8gg88gg5553g§ 1 


CO 



) TO o6 00 00 00 oi 03 < 



c<iMeocO'*-*'*-*-*-*LO 
^ I ^ th 55 ^ CO :^ ^'(A lo'ift CO co^cot-t-t-ttt~ttrt 



sill§ililll§iillliiiiil |. 



O lA O Ift O 15 
CO CO ■>* ■* in in 



o Ift o ic c 



I O IS o m o m Q I 
> o o 1-1 i-i <M <^q CO ( 



TABLE 13. 
Properties of Air with Moisture under Pressure of 
Atmosphere.* 



One 





d 




g 


Mixtures of air saturated 










-u 




.s 


with vapor 






O a; 

— f-1 








Weight of cubic 






T3 




§8 


-b^ 


d 


a 


foot of the 






is 


a 


."S 


fe ^ 


-^=5 


■" 


tH,Q Sh" 


mixture. 






li 


B 

o 
P. 

s 


19 

o S 


tit 

o £i 
."IS 


II 

> a 

Si 


S e g 

Hi 

fii 




03 
O u 


B 

C3 03 


•Hi 

OG.S 


S s 




w 

"^ o 


o . 

■|.s 

■SB 

II 


II 
II 

e a; 

6g 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 





.935 


.0864 


0.044 


29.877 


.0863 


.000079 


.086379 


.00092 


1092.40 




48.5 


12 


.960 


.0842 


0.074 


29.849 


.0840 


.000130 


.084130 


.00115 


646.10 




50.1 


22 


.980 


.0824 


0.118 


29.803 


.0821 


.000202 


.0^.302 


.00245 


406.40 




51.1 


82 


1.000 


.0807 


0.181 


29.740 


.0802 


.000304 


.080504 


.00379 


263.81 


3289'0 


52.0 


42 


1.020 


.0791 


0.267 


29.6.54 


.0784 


.000440 


.078840 


.00561 


178.18 


22.52.0 


53.2 


52 


1.041 


.0766 


0.388 


29.533 


.0766 


.000627 


.077227 


.00819 


122.17 


1.595.0 


.54.0 


60 


1.057 


.0764 


0..522 


29.399 


.0751 


.000&30 


.075252 


-.012.51 


92.27 


1227.0 


.55.0 


62 


1.061 


.0761 


0.5.56 


29.365 


.0747 


.000881 


.075581 


.01179 


84.79 


1135.0 


55.2 


70 


1.078 


.0750 


0.7.54 


29.182 


.0731 


.001153 


.073509 


.01780 


64.59 


882.0 


56.2 


72 


1.082 


.0747 


0.785 


29.136 


.0727 


.001221 


.073921 


.01680 


59.54 


819.0 


56.3 


82 


1.102 


.0733 


1.092 


28.829 


.0706 


.001667 


.072267 


.02361 


42.35 


60O.0 


57.2 


9-2 


1.122 


.0720 


1..501 


28.420 


.0684 


.002250 


.070717 


.03289 


30.40 


444.0 


58.4 


lOO 


1.139 


.0710 


1.929 


27.992 


.0664 


.002848 


.069261 


.04495 


23.66 


3.56.0 


59.1 


102 


1.143 


.0707 


2.036 


27.885 


.0659 


.002997 


.068897 


.04.547 


21.98 


334.0 


59.5 


112 


1.163 


.0694 


2.731 


27.190 


.0631 


.003946 


.067042 


.06253 


15.99 


253.0 


60.6 


122 


1.184 


.0682 


3.621 


26.300 


.0599 


.005142 


.06.5046 


.08584 


11.65 


194.0 


61.7 


132 


1.204 


.0671 


4.7.52 


25.169 


.0.564 


.006639 


.063039 


.11771 


8.49 


151.0 


62.5 


142 


1.224 


.0660 


6.165 


23.756 


.0524 


.008473 


.060873 


.16170 


6.18 


118.0 


63.7 


152 


1.245 


.0649 


7.930 


21.991 


.0477 


.010716 


.058416 


.22465 


4.45 


93.3 


64.7 


162 


1.265 


.0638 


10.099 


19.822 


.0423 


.013415 


.05.5715 


.31713 


3.15 


74.5 


65.8 


172 


1.285 


.0628 


12.7.58 


17.163 


.0360 


.016682 


.052682 


.46338 


2.16 


59.2 


66.9 


182 


1.306 


.0618 


15.960 


13.961 


.0288 


.020536 


.049336 


.71300 


1.402 


48.6 


68.0 


192 


1.326 


.0609 


19.828 


10.093 


.0205 


.025142 


.045642 


1.22643 


.815 


39.8 


69.0 


202 


1.347 


.0600 


24.450 


5.471 


.0109 


.030545 


.041445 


2.80230 
In- 
finite 


.357 


32.7 


70.0 


212 


1.367 


.0591 


29.921 


O.OOO 


.0000 


.036^0 


.036820 


.000 


27.1 


71.1 



Carpenter's H. & V. B. and Sturtevant's Mech. Draft. 



417 



TABLE 14. 
DcAV-Points of Air According' to Its Hygrometric State.* 













Relative moisture 






Temp. 










































90% 


80% 


70% 


60% 


50% 


C. 


F. 


C. 


F. 


C. 


F. 


C. 


F. 


•C. 


F. 


C. 


F. 





82.0 


-1.5 


29.3 


— 3.0 


26.6 


— 4.9 


23.2 


— 6.5 


20.3 


— 9.2 


15.4 


2 


35.6 


0.9 


33.6 


— 0.9 


30.4 


— 2.5 


27.5 


— 4.8 


23.4 


— 7.1 


19.2 


4 


3&.2 


2.4 


36.3 


• 0.9 


33.6 


— 0.9 


30.4 


— 2.9 


26.8 


— 5.3 


22.5 


6 


42.8 


4.5 


40.1 


2.9 


37.2 


0.9 


33.6 


— 1.3 


29.7 


- 3.7 


25.3 


8 


46.4 


6.4 


43.5 


4.5 


40.1 


2.7 


36.9 


0.6 


83.1 


— 1.9 


28.6 


10' 


50. 


8.5 


47.3 


6.8 


44.2 


4.5 


40.1 


2.5 


36.5 


0.0 


.32.0 


12 


53.6 


10.5 


50.9 


8.5 


47.3 


6.8 


44.2 


4.3 


39.7 


2.0 


35.6 


14 


57.2 


12.3 


54.1 


10.5 


50.9 


8.5 


47.3 


6.2 


43.2 


3.7 


38.7 


10 


60.8 


14.4 


57.9 


12.6 


54.7 


10.5 


50.9 


8.3 


46.9 


5.6 


42.1 


18 


64.4 


16.5 


61.7 


14.6 


58.3 


12.4 


54.3 


10.0 


50.0 


7.4 


45.3 


20 


68.0 


18.3 


64.9 


16.5 


61.7 


14.4 


57.9 


11.9 


53.4 


9.2 


48.6 


22 ' 


71.6 


20.3 


68.5 


18.4 


65.1 


16.3 


61.3 


13.7 


56.7 


11.6 


52.8 


24 


75.2 


22.2 


72.1 


20.5 


68.9 


18.4 


65.1 


15.6 


60.0 


. 13.0 


55.4 


26 


78.8 


24.4 


75.9 


22.2 


72.1 


20.1 


68.2 


17.6 


63.6 


14.7 


58.5 


28 


82.4 


26.3 


79.3 


24.2 


75.6 


22.0 


71.6 


19.5 


67.1 


17.5 


63.5 


30 


86.0 


28.3 


82.9 


26.3 


79.3 


23.9 


75.0 


21.5 


70.7 


18.3 


[ 64.9 



70lli 


"""^ 
















^ 














"4^ 


% 










nn^ 








'^^ 


=*v. 






1 
20 










^ 


^=5-- 
















=::5^ 


BO e 


5 -7 


7 


»=.., J 


8 


s 


9 


8 



* Bulletin 21, Int. Ass'n of Refrig. 

Psychroinetric Charts Recent Tests. 

In recent years a highly technical study of humidity 
and its control has been made by Mr. Willis H. Carrier. Fig. 
A shows, merely for the sake of comparison, how closely his 

results checked the earlier 
values obtained by the Gov- 
ernment Weather Bureau. The 
following- charts. Figs. B and 
C, summarize the results of 
Mr. Carrier's experiments 
orv-bulb"" "= '° "' -p.g. c is a part of Fig. B 
^^S- ^- drawn to a larger scale. 

As one illustrati-on of the use of the chart, refer to Fig. 
C with, air at 40 degrees and 40 per cent, humidity. If this 
air be heated to 100 degrees without addition of moisture 
it will be seen by interpolation that the humidity drops to 
about 8 per cent. If the same be heated to 100 degrees 
and enough moisture be added to keep the relative humid- 
ity at 40 per cent., then the absolute humidity changes from 
15 grains to 120 grains per pound of air. These figures 
may be reduced to grains per cubic foot by dividing by the 
volume per pound as given in the second column and will 
be found to check closely with those given by Fig. 7 and 
Table 9. Almost any other points relating to changes in 
volume, humidity and contained heat may be easily worked 



out by these curves. 



418 



s 














§ 




% 




§ 




s 




s? 




s 












^ 




/ 












yj 


/ 


/^ 


' } 


J 


/ 


// 


/^ 


// 


V 


// 


A7 




// 






/// 


/=^^ 












1 


^/ 


y 


/ 


1 


/) 


^/ 




// 


y 


// 




'/</ 










/// 


/. 




1 




^ 


A 


/ 




\l 


/ 


i() 






// 






II 












/// 


/"" 


Y 






> 




/ 


'S 


V 




A 


(/ 


y 






// 


















/// 


/n 














/ 


/S 




/^ 


'nV 






/ 


















y^/. 


/f 












^ 


^/ 




)^ 


' / 


/I 






/yj 


















7/7 


/ 














y 


/^ 




J 


A 


J/ 






// 


















'III 


r 










^ / 


s^ 




1% 


// 


A 






u 


















ihl 


1 










V 




^s 


/ , 




1 


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7 






'Y 


















'hi 


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\ 


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1 1 


n 


















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Q 


A 


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W 




h/i 


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W 


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f^ 












Wh 




ij/ii 


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K 






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'rill 


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^ 


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Y 
















'11'/ 


/ 




















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'ml 


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1 
























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r 


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— 


























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'rlfi 


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f 






























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vv 




w 


W 


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i 




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M 


mu/ 


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fflfflr 


1 




































A 




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wlB 


M" 










fut. 


i/au 


/oc 


t/M 


l/l SJ 


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JOtf^ 




















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mfflp 


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1 


m/M 






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jie. 






p,m 


4M:> 


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7^ 


p/«* 




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s™3| 


/"^ 


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Dui^ 


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tan 






j,el 


pit/ 


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4PU 


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ff^fl 


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^\ 




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^ 






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S 


V/Ji 


tfj 


yqn 


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1 




1 




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X 


ifflv 




w 






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12 


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t 




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g 








« 




'2 





TABLE 15. 
Fuel Value of American Coals.* 



Coal 
name or locality 



Fuel value per pound 
of coal 



B. t. u. 
calcu- 
lated 



B. t. u. 
by calor- 
imeter 



Theoret- 
ical evap- 
oration 
in lbs. 
from and 

at 212 
deg. r. 



ARKANSAS. 

Spadra Johnson Co. 

Coal Hill, Johnson Co. 

Huntington Co. 

Lignite 

COLORADO. 

Lignite _- 

Lignite, slack 

ILLINOIS. 

Big Muddy, Jackson Cto. 

Colchester, Slack 

Giliespie Macoupin Co. 

Mercer Co. 

INDIANA. 

Block 

Cannel 

IOWA. 

Good Cheer 

KENTUCKY. 

Caking 

Cannel 

Lignite 

MISSOURI. 

Bevier Mines 

NEW MEXICO. 
Coal 

OHIO. 

Briar HiU, Mahoning Co 

Hocking Valley 

PENNSYLVANIA. 

Anthracite 

Anthracite, pea 

Pittsburgh (average) 

Youghiogheney 

TEXAS. 

Fort Worth 

Lignite 

WEST VIRGINIA. 

Pocahontas 

New River 

* Sturtevant's "Mechanical Draft 



14,420 



9,215 

13,560 
8,500 



14,020 
13,097 



14,391 
15,198 
9,326 



13,714 
13,414 

14,199 
12,300 



12,962 
14,200 



11,812 
11,756 



11,781 
9.035 



13,123 



8,702 



9,890 
11,756 



13,104 
12,936 



9,450 



14,273 



14.90 
12.22 
12.17 
9.54 

14.04 
8.80 

12.19 
9.35 
10.09 
13.58 

14.50 
13.56 



14.89 
16.76 
9.65 

10.24 

12.17 

14.20 
13.90 

14.70 
12.73 
13.46 
13.39 

9.78 
13.41 

14.71 
14.70 



421 



TABLE 16. 
Capacities of Cliiinneys.* 



Inside 
diam- 




Maximum sq. ft. of cast iron radiating 

surface and B. t. u. for a flue of the 

given diameter and height 


lined 
flue, 
inches 


25 
feet 
high 


36 
feet 
high 


49 
fe«t 
high 


64 
feet 
high 


81 
feet 
high 


100 
feet 
high 




Steam 


146 

243 

36500 

228 

379 

5700O 

327 

544 

81750 

445 

742 

111250 

582 

969 

145500 

909 

1514 

227250 

1587 

2561 

384250 

2327 

3878 

561750 


175 

291 

43750 

273 

455 

68250 

392 
653 

980OO 

534 

890 

133500 

698 

1163 

174500 

1090 

1817 

272500 

1844 

3073 

461000 

2792 

4653 

698000 


204 

340 

51000 

319 
531 

79750 

457 

762 

114250 

623 

1088 

155750 

814 
1357 

20^3600 

1272 

2120 

318000 

2151 

3586 

537750 

3257 

5429 

814250 


233 

388 
58250 

364 

607 

9100O 

523 

871 

130750 

712 

1187 

178000 

930 

15.51 

232500' 

1454 

2423 

363500 

2458 

4098 

614500 

3722 

6204 

930500 


262 

437 

65500 

410 

683 

102500 

588 

980 

147000 

801 
1385 

200250 

1047 

1745 

261750 

1636 

2726 

409000 

2766 

4610 

691500 

4188 

6980 

1047000 


291 

485 
72750 

455 


6 


Hot water 

B. t. u. 

Steam 


7 


Hot water 

B. t. u. 

Steam 


758 
113750 

653 


8 


Hot water 

B. t. u. 

Steam 


1083 
163250 

890 


9 


Hot water 

B. t. u. 

Steam 


1483 

222500 

1163 


10 


Hot Avater 

B. t. u. 

Steam 


1938 
290750 

1817 


12 
15 


Hot water 

B. t. u. 

Steam 

Hot water 

B. t. u. 

Steam 


3028 
454250 

3073 

5122 

768250 

4658 


18 


Hot water 

B. t. u. 


7755 
1163250 



Radiation is calculated at 250 B. t. u. steam, 150 B. t. u. water. 



TABLE 17. 
Excelsior Double Wall Stack.i 



No. 


Sizes, Inches 


Area 
Stack, 
Sq. In. 


Collar 

Diameter, 

Inches 


Nominal 


Inside 


Outside 


7 
8 
9 
12 


4x11 
4x13 
4x14 
6X:13 


3x10 
3x12 
3x13 
5x12 


3%xl0% 
3%xl2% 
3%xl3% 
5%xl2% 


30 

39 
60 


8 and 9 

8, 9 and 10 

9 and 10 
9 and 10 



The Model Boiler Manvial. 
t Excelsior Furnace Co. 



422 



TABLE 18. 
Elqualization of Smoke Flues — Commercial Sizes.* 



Inside 


Brick flue 


Eectangular 


Outside 


diameter 


not lined 


lined flue 


iron 


lined flue 


well built 


outside of tile 


stack 


6 


81/2X81/2 




8 


7 


81/2X81/2 


7x7 


9 


8 


81/2X81/2 


81/2X81/2 


10 


9 


81/2X13 


81/2XI3 


11 


10 


81/2X13 


8I/2XI3 


12 


12 


13x13 


13x13 


14 


15 


13x17 


13x18 


17 


18 


17x211/2 


18x18 


20 



Round flue tile lining- is listed by its inside measurement. 
Roetang-ular lining by outside measurement. 



TABLE 19. 
Dimensions of Registers. 





Nominal 


Effective 






Size of 


area of 


area of 




Extreme 


opening, 


opening, 


opening, 


Tin box size, 


dimensions of 


inches 


square 


square 


inches 


register face. 




inches 


inches 




inches 


6x 10 


60 


40 


&J% X l(h\ 


7H- X llf^ 


8x10 


80 


53 


8% X 10% 


93/4 X 11% 


8x12 


96 


64 


8% X 12% 


9% X 13% 


8x15 


120 


80 


.8%xl5% 


9% X mi 


9x12 


108 


72 ■ 


&h X mh 


107/8 X 137/8 


9x14 


126 


84 


9^6 X U\i 


107/8 X 1.57/8 


10x12 


120 


80 


lOii X 12U 


nil X i3i| 


10x14 


140 


93 


m-e X 14H 


nil X i5it 


10x16 


160 


107 


m^ X 16ii 


11-il X 177/8 


12x15 


180 


120 


12% X 153^ 


14iV X 17 


12x19 


228 


1.52 


12i% X 19% 


14tV X 21 


14x22 


308 


205 


147/8 X 227/8 


16y4 X 24y4 


15 X 25 


375 


2.50 


isys X 257/8 


17% X 2714 


16x20 


320 


213 


167/8 X 207/8 


18i^^ X 22t% 


16x24 


384 


2.56 


167/8 X 247/8 


im X 26T^ir 


20x20 


400 


267 


20i| X 20M 


22% X 223/8 


20x24 


480 


320 


20-f X 24i| 


22% X 263/8 


20x26 


520 


347 


20i| X 26i| 


22% X 283/8 


21x29 


609 


403 


2m X mi 


23% X 31% 


27x27 


729 


486 


2711 X 27i| 


29% X 29% 


27x38 


1026 


684 


27t| X 38i| 


29% X 40% 


30x30 


900 


600 


30t| X soil 


32% X 32% 



Dimensions of different makes of registers vary slightly. 
are for Tuttle & Bailey manufacture. 
* The Model Boiler Manual. 



The above 



423 



TABLE 20. 

Capacities of W^arin Air Furnaces of Ordinary Construction 

in Cubic Feet of Space Heated.* 



Divided space 


Fire-pot 


Undivided space 


+ 10° 


0° 


—10° 


Diam. 


Area 


+10° 


0° 


—10° 


1200O 


10000 


8000 


18 in. 


1.8sq. ft. 


17O0O 


14000 


12000 


14000 


12O0O 


10000 


20 " 


2.2 " 


220OO 


17000 


14000 


17000 


14000 


12000 


22 " 


2.6 " 


26000 


22000 


170O0 


23Gm 


18000 


14000^ 


24 " 


3.1 " 


30000 


26000 


22000 


26000 


22000 


1800O 


26 " 


3.7 " 


35000 


30O0O 


26000 


30000 


26000 


22000 


28 " 


4.3 " 


40000 


35000 


30000 


35000 


30000 


2600O 


30 " 


4.9 " 


50000 


40000 


35000 



TABLE 21. 
Capacities of Hot-Air Pipes and Registers.f 









Oubic feet 








Equivalent 


Equiv- 


of space 


Cubic feet 


Cubic feet 


Size of 


area in 


alent in 


on first 


on second 


on third 


register 


round or 


square or 


floor same 


floor 


floor 




leader pipe 


riser pipe 


will heat 






6X8 


6 in. 


4x8 


400 


450 


500 


8x8 


7 " 


4x10 


450 


500 


560 


8x10 


8 " 


4x10 


500 


850 


880 


8x12 


8 " 


4x11 


800 


lOOO 


1050 


9x12 


9 " 


4x12 


1050 


1250 


1320 


9x14 


9 " 


4x14 


1050 


1350 


1450 


10x12 


10 " 


4x14 


1500 


1650 


180O 


10x14 


10 " 


6x10 


1800 


2000 


220O 


10x16 


10 " 


6X10 


1800 


2000 


2200 


12X14 


12 " 


6x12 


2200 


2300 


2500 


12x15 


12 " 


6x12 


2250 


230O 


2500 


12x17 


12 " 


6x14 


2300 


2600 


2800 


12x19 


12 " 


6x14 


2300 


2600 


2800 


14x18 


14 " 


6x16 


2800 


3000 


3200 


14x20 


14 " 


6x16 


2900 


3000 


3200 


14x22 


14 " 


8x16 


3000 


3200 


3400 


16x20 


16 " 


8x18 


3600 


4000 


4250 


16x24 


16 " 


8x18 


370O 


4000 


4250 


20x24 


18 " 


10X20 


4800 


5400 


5750 


20x26 


20 " 


10x24 


6000 


7000 


7450 



* Federal Furnace League Handbook. 
t Kidder's Arch, and B'ld'rs Pocket-Book. 



TABLE 22. 
Air Heating Capacity of Warm Air Furnaces.* 







Total 








cross sec. 




Fire-pot 


Casing 


area of 


No. and size of heat pipes that 






heat 


may be supplied 






pipes 




Diam 


Area 


Diam. 


180 sq. in. 




18 in. 


1.8 sq. ft. 


30"-32" 


3-9" or 4-8" 


20 " 


2.2 " 


34"-36" 


280 •' 


2-10" and 2-9" or 3-9" and 2-8" 


22 " 


2.6 " 


36"-40" 


360 " 


3-10^' and 2-9" or 4-9^' and 2-8" 


24 " 


3.1 " 


40"-44" 


4'70 " 


3-10", 1-9" and 2-8" or 2-10" and 5-8" 


26 " 


3.7 " 


44"-50" 


565 " 


5-10" and 3-9" or 3-10", 4-9" and 2-8" 


28 " 


4.3 " 


48"-56" 


650 " 


2-12", 3-10" and 3-9" or 5-10", 3-9" and 2-8" 


30 " 


4.9 " 


52"-60" 


730 " 


3-12", S-ir and 3-9" or 5-10", 5-9" and 1-8" 



TABLE 23. 

Sectional Area (Square Inches) of Vertical Hot Air Flues, 

Natural Draft, Indirect System.t 

Outside temperature 50° F. Flue temperature 90° F. 







STEAM 






WATER 




Sq. ft. 


















cast iron 


















radiation 




Ti 




;a 




-C 




X3 




+3 >. 


a >. 


-p >. 


"E >> 


-ij {>. 


s >> 


'S >> 


t, >. 






O t-^ 


^ t-i 


;3 fH 


XD ^ 


-^ 


'-I Sh 


!3 f-i 




II 


U 


05 


■el 


m m 


u 


1° 


Oto 50 


100 


75 


63 


60 


75 


63 


60 


60 


50 " 75 


150 


113 


94 


■ 80 


113 


94 


80 


80 


75 " 100 


20O 


150 


125 


100 


150 


125 


100 


100 


lOO " 125 


250 


188 


156 


125 


188 


156 


125 


125 


125 " 150 


300 


225 


188 


150 


225 


188 


150 


150 


150 " 175 


350 


263 


219 


175 


263 


219 


175 


175 


175 " 200 


400 


300 


250 


200 


300 


250 


200 


200 


200 " 225 


450 


338 


281 


225 


338 


281 


225 


225 


225 " 250 


500 


375 


313 


250 


375 


313 


250 


250 


250 " 275 


550 


413 


344 


275 


413 


344 


275 


275 


275 " 300 


600 


450 


375 


300 


450 


375 


300 


300 


300 " 325 


650 


488 


406 


325 


488 


406 


325 


325 


325 " 350 


TOO 


525 


438 


350 


525 


438 


350 


350 


350 " 875 


750 


563 


469 


375 


563 


469 


375 


375 


375 " 400 


800 


600 


500 


400 


600 


500 


40O 


40O 


Velocity 


















feet per sec. 


21/2 


41/2 


. 51/2 


61/2 


m 


21/2 


4 


4 


Effective area 


















of reg-ister. 


1.00 


1.50 


1.83 


2.17 


1.00 


1.00 


1.33 


1.33 


Factor for 



















* Federal Furnace League Handbook. 
+ The Model Boiler Manual. 



TABLE 24. 
Sheet Metal Dimensions and Weights. 





Approximate 


Wt. per sq 


. ft. in lbs. 




Decimal 


Iron 


Steel 


U. S. Gage 


gage 


millimeters 


480 lbs. per 
cu. ft. 


489.6 lbs. per 
cu. ft. 


numbers 


0.002 


0.05 


0.08 


0.082 




0.004 


0.10 


0.16 


0.163 




0.006 


0.15 


0.24 


0.245 


38-39 


0.008 


0.20 


0.82 


0.326 


84-35 


0.010 


0.25 


0.40 


0.408 


32 


0.012 


0.30 


0.48 


0.490 


30-31 


0.014 


0.36 


0.56 


0.571 


29 


0.016 


0.41 


0.64 


0.653 


27-28 


0.018 


0.46 


0.72 


0.734 


26-27 


0.020 


0.51 


0.80 


0.816 


25-26 


0.022 


0.56 


0.88 


0.898 


25 


0.025 


0.64 


1.00 


1.020 


24 


0.028 


0.71 


1.12 


1.142 


23 


0.032 


0.81 


1.28 


1.306 


21-22 


0.036 


0.91 


1.44 


1.469 


20-21 


0.040 


1.02 


1.60 


1.632 


19-20 


0.045 


1.14 


1.80 


1.836 


18-19 


0.050 


1.27 


2.00 


2.040 


18 


0.055 


1.40 


2.20 


2.244 


17 


O.06O 


1.52 


2.40 


2.448 


16-17 


0.065 


1.65 


2.60 


2.652 


15-16 


0.070 


1.78 


2.80 


2.856 


15 


0.075 


1.90 


3.00 


3.060 


14-15 


0.080 


2.08 


3.20 


3.264 


13-14 


0.085 


2.16 


3.40 


3.468 


1.3-14 


O.09O 


2.28 


3.60 


3.672 


13-14 


0.095 


2.41 


3.80 


3.876 


12-13 


0.1 OO 


2.54 


4.0O 


4.080 


12-13 


0.110 


2.79 


4.40 


4.488 


12 


0.125 


3.18 


5.00 


5.100 


11 


0.135 


3.43 


5.40 


5.508 


10-11 


0.150 


3.81 


6.00 


6.120 


9-10 


0.165 


4.19 


6.60 


6.732 


8-9 


0.180 


4.57 


7.20 


7.344 


7-8 


O.20O 


5.08 


8.00 


8.160 


6-7 


0.220 


5.59 


8.80 


8.976 


4-5 


0.240 


6.10 


9.60 


9.792 


3-4 


0.250 


6.35 


10.00 


10.200 


3 



For weights of galvanized iron, multiply weight, black, by:— 
No. 28 No. 26 No. 24 No. 22 No. 20 No. 18 No. 16 



1.25 



1.13 



1.07 



TABLE 25. 

Weight of Round Galvanized Iron Pipe and ElboTrs of the 

Proper Gages for Heating and Ventilating Work. 





O 

la 






III 


2| 
Is 




o 

.5 ft 
Oft 


1^1 

•6o..S 




h 
III 


^5 




3 


9.43 


7.1 


0.7 


0.4 




36 


113.10 


1017.9 


17.2 


124.4 




4 


12.57 


12.6 


1.1 


0.9 




37 


116.24 


1075.2 


17.8 


131.4 


No. 28 


5 


15.71 


19.6 


1.2 


1.2 




38 


119.38 


1134.1 


18.2 


139.4 


0.78 


6 


18.85 


28.3 


>.4 


1.7 




39 


122.52 


1194.6 


18.7 


146.0 




7 


21.99 


38.5 


1.7 


2.3 




40 


125.66 


1256.6 


19.1 


152.9 




8 


25.13 


50.3 


1.9 


2.9 


No. 20 


41 


128.81 


1320.6 


19.6 


160.7 














1.66 


42 

43 


131.95 
135.09 


1385.4 
1452.2 


20.1 
20.6 


168.6 




9 


28.27 


63.6 


2.4 


4.3 


176.7 




10 


31.42 


78.5 


2.7 


5.3 




44 


138.23 


1520.5 


21.0 


185.0 


No. 26 


11 


34.56 


95.0 


2.9 


6.4 




45 


141.37 


1590.4 


21.5 


193.4 


0.91 


12 
13 
14 


37.70 
40.84 
43.98 


113.1 
132.7 
153.9 


3.2 
3.4 
3.7 


7.6 
8.9 
10.4 




46 


144.51 


1661.9 


22.0 


202.2 






47 


147.65 


1734.9 


29.2 
















274.3 




15 


47.12 


176.7 


4.5 


13.5 




48 


150.80 


1809.6 


29.8 


286.6 




16 


50.27 


201.1 


4.7 


15.1 




49 


153.94 


1885.7 


30.4 


298.8 


No. 25 


17 


53.41 


227.0 


5.0 


17.0 




50 


157.08 


1963.5 


31.0 


309.9 


1.03 


18 


56.55 


254.5 


5.3 


19.1 




51 


160.22 


2042.8 


31.6 


322.5 




19 


59.69 


283.5 


5.6 


21.4 


No. 18 


52 


163.36 


2123.7 


32.2 


335.1 




20 


62.83 


314.2 


6.0 


23.9 


2.16 


53 


166.50 


2206.2 


33.0 


349.7 
















54 


169.65 


2290.2 


33.6 


463.4 




21 


65.97 


346.4 


7.0 


29.6 




55 


172.79 


2375.8 


34.4 


377.2 




22 


69.12 


380.1 


7.3 


32.3 




56 


175.93 


2463.0 


34.9 


390.7 


No. 24 


23 


72.26 


415.5 


7.7 


35.6 




57 


179.07 


2551.8 


35.6 


405.1 


1.16 


24 


75.40 


452.4 


8.0 


38.6 




58 


182.21 


2642.1 


36.1 


418.8 




25 


78.54 


490.9 


8.3 


41.7 




59 


185.35 


2734.0 


36.7 


433.1 




26 


81.68 


530.9 


8.7 


45.1 




60 


188.50 


2827.4 


37.4 


448.6 




27 


84.82 


572.6 


10.9 


59.1 
















28 


87.97 


615.7 


11.4 


64.2 




61 


191.64 


2922.5 


46.7 


569.7 




29 


91.11 


660.5 


11.8 


68.6 




62 


194.78 


3019.1 


47.5 


589.0 


No. 22 


30 


94.25 


706.9 


12.2 


73.4 




63 


197.92 


3117.3 


48.3 


608.6 


1.41 


31 


97.39 


754.8 


12.6 


78.3 


No. 16 


64 


201.06 


3217.0 


49.1 


628.5 




32 


100.53 


804.3 


13.0 


83.4 


2.66 


66 


207.34 


3421.2 


50.5 


666.6 




33 


103.67 


855.3 


13.5 


88.9 




68 


213.63 


3631.7 


52.1 


708.6 




34 


106.84 


907.9 


13.9 


94.3 




70 


219.91 


3848.5 


53.6 


750.4 




35 


109.96 


962.1 


14.3 


99.9 




72 


226.19 


4071.5 


55.1 


793.4 



427 



TABLE 26. 
Specific Heats, Coefflicieiits of Expansion, Coefficients of Trans- 
mission, and Fusing:-Points of Solids, liiquids or Gases. =*= 



SUBSTANCE 


Specific 
heats 


Coefficient 

of 
expansion 


Coefficient 
of trans- 
mission 


Fusion 
points, 
degrees 


Antimony 

Copper 


0.0508 
O.0951 
0.0324 
0.1138 
0.1937 
0.1298 
0.0314 
0.0324 
0.0570 
0.0562 
0.1165 
0.1175 

'O'O056" 
0.0039 
0.5040 
0.2026 
0.2410 
0.1970 
0.1887 
1.0000 
0.0'333 
O.700O 


.00000602 
.00000955 
.00001060 
.0O0O0S95 
.00000478 
.00000618 
.00001580 
.00000530 
.00001060 
.00001500 
.00000600 
.00000680 
.00000003 
.00001633 
.00001043 
.00000375 
.00006413 
.00007860 
.00002313 
.00012530 
.00008806 
.0'00O3333 
.00015151 


.00022 
.00404 


815 
1949 


Gold 


1047 


Wrought iron 


.00080 
.0000008 
.000650 
.00045 


2975 


Glass — -— 


1832 




2102 


Lead 

Platinum 


621 

3452 


Silver 

Tin _ 


.00610 
.00084 
.00062 
.00034 


1751 
446 


Steel (soft) 

Steel (hard) 


2507 
2507 


Nickel steel 36% 




Zinc 

Brass 


.00170 
.00142 
.000024 


787 
1850 


Ice 


32 


Charcoal 

Aluminum 


.000002' 
.00203 


1213 


Phosphorus 




Water 


.000008 

.00011 

.000002 








Alcohol (absolute) 







Con- 
stant 
pres- 
sure 


Con- 
stant 
volume 


Coeffi- 
cient of 
cubical 
expansion 
atl 
atmos. 






Air 


0.23751 
0.21751 
3.40900' 

0.24380 

0.4805 

0.2170 


0.16847 

0.15507 

2.41226 

0.17273 

0.346 

0.1535 


.00'3671 
.003674 
.003660 
.003668 
.003726 


.0000015 
.0000012 
.0000012 
.0000012 

?oooooi22 




Oxygen 




Hydrogen 

Nitrogen 

Superheated steam __ 
Carbonic acid 





Kent and Suplee. 



428 



TABLE 27. 



Pressure in Ounces, per Square Inch, Corresponding^ to 
Various Heads of Water, in Inches.* 











Decimal parts of an inch 








Head 










































in 






















inches 


.0 


.1 


.2 


.3 


.4 


.5 


.6 


.7 


.8 


.9 







.06 


.12 


.17 


.23 


.29 


.35 


.40 


.46 


.52 


1 


.58 


.63 


.69 


.75 


.81 


.87 


.93 


.98 


1.04 


1.09 


2 


1.16 


1.21 


1.27 


1.33 


1.39 


1.44 


1.50 


1.56 


1.62 


.1.67 


3 


1.73 


1.79 


1.85 


1.91 


1.96 


2.02 


2.08 


2.14 


2.19 


2.25 


4 


2.31 


2.37 


2.42 


2.48 


2.. 54 


2.60 


2.66 


2.72 


2.77 


2.83 


5 


2.89 


2.94 


3.0O 


3.06 


3.12 


3.18 


3.24 


3.29 


3.35 


3.41 


6 


3.47 


3.52 


3.58 


3.64 


3.70 


3.75 


3.81 


3.87 


3.92 


3.98 


7 


4.04 


4.10 


4.16 


4.22 


4.28 


4.33 


4.39 


4.45 


4.50 


4.56 


8 


4.62 


4.67 


4.73 


4.79 


4.85 


4.91 


4.97 


5.03 


5.08 


5.14 


9 


5.20 


5.26 


5.31 


5.37 


5.42 


5.48 


5.54 


5.60 


5.66 


5.72 



TABLE 28. 
Height of Water Column, in Inches, Corresponding to Pres- 
sures, in Ounces, per Square Inch.* 









Decimal parts of an ounce 




Pressure 






































in oimces 






















per square 


.0 


.1 


.2 


.3 


.4 


.5 


.6 


.7 


.8 


.9 


inch 



























.17 


.35 


.52 


69 


.87 


1.04 


1.21 


1.88 


1.56 


1 


1.73 


1.90 


2.08 


2.25 


2.42 


2.60 


2.77 


2.94 


3.11 


3.29 


2 


3.46 


3.63 


3.81 


3.98 


4.15 


4.33 


4.50 


4.67 


4.84 


5.01 


3 


5.19 


5.36 


5.54 


5.71 


5.88 


6.06 


6.23 


6.40 


6.. 57 


6.75 


4 


6.92 


7.09 


7.27 


7.44 


7.61 


7.79 


7.96 


8.13 


8.30 


8.48 


.5 


8.65 


8.82 


9.00 


9.17 


9.34 


9.52 


9.69 


9.86 


10.03 


10.21 


6 


10.38 


10-55 


10.73 


10.90 


11.07 


11.26 


11.43 


11.60 


11.77 


11.95 


7 


12.11 


12.28 


12.46 


12.63 


12.80 


12.97 


13.15 


13.32 


13.49 


13.67 


8 


13.84 


14.01 


14.19 


14.36 


14.. 53 


14.71 


14.88 


15.05 


15.22 


15.40 


9 


15.57 


15.74 


15.92 


16.09 


16.26 


16.45 


16.62 


16.76 


16.96 


17.14 



* Suplee's M. E. Reference Book. 



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430 



TABLE 30. 
Expansion of Wrought-Iron Pipe on the Application of Heat. 



Temp, air 














when 




Increase in lengtla in inches 


per 100 feet 




pipe 






when heated to 








is fitted 














Beg. F. 


160 


180 


200 


212 


220 


- 228 


240 


274 





1.28 


1.44 


1.60 


1.70 


1.76 


182 


1.02 


2.19 


32 


1.02 


1.18 


1.34 


1.44 


1.50 


1.57 


1.66 


1.94 


50 


.88 


1.04 


1.20 


1.30 


1.36 


1.42 


1.52 


1.79 


70 


.72 


.88 


1.04 


1.14 


1.20 


1.26 


1.36 


1.63 



TABLE 31. 
Tapping- LLst of. Direct Radiators.f 

STEAM. 



ONE-PIPE WORK 


T^^O-PIPE WORK 


Eadiator area 
square feet 


Tapping- diam- 
eter-inches 


Radiator area 
square feet 


Tapping diam- 
eter — inches 


0—24 

24—60 

60—100 

100 and above 


1 

11/4 
11/2 
2 


— 48 

48 — 96 

96 and above 


1 X % 

11/4x1 

11/2x11/4 


WATER. 
Tapped for supply and return. 


Radiator area 
square feet 


Tapping- diameter 
inches 


— 40 

40 — 72 

72 and above 


1 

11/2 



* Holland Heating Manual, 
t American Radiator Co. 



131 



TABLE 32. 
Pipe Equalization. (See also Table 21) 



eo --I (M 

CM • ■ 

--; CM CO 

'M CO m 



C-1 ^ ra GO O (M ■ 



This table shows the relation of the 
combined area of small round warm 
air ducts or pipes to the area of one 
larg-e main duct. 

The bold figures at the top of the 

column represent the diameters of 

the small pipes or ducts; those in 

the left-hand vertical columns 

are the diameters of the main 

pipes. The small figures show 

the number of small pipes that 

each niain duct will supply. «^ 

Example. — To supply sixteen ^ ""! 

10-inch pipes: Refer to column ,-h , „ „ 

having 10 at top; follow o .-Hco'j^ot- 

down to small figure 16, '^ ^' ^^ ,-i ^ ,_; 

thence left on the hori- 
zontal line of the bold- 
face figiu-e in the 
outside colimin, and 
we find that one 
30-inch main will 
supply air for 
the sixteen 
10 - inch 
pipes. 

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432 



TABLE 33. 

Sizes of Hot- Water Mains. 

Open Tank System. 

Assumed Length 100 feet.f 





Capacity, square feet of direct radiation 


Pipe diam. 










inches 


Two-pipe* 


One-pipe 


Attic 




up feed 


up feed 


main 


11/4 


100 


50 


150 


11/2 


160 


75 


225 


2 


275 


125 


375 


21/2 


375 


2-25 


540 


3 


600 


400 


&00 


31/2 


80O 


500 


1800 


4 


1100 


700 


1800 


5 


190O 


1200 


3200 


6 


SOOO 


2000 


5000' 


7 


4500 


. 3000 


7200 


8 ■ 


6000 


40O0 


10000 



For mains over 100' reduce capacity in the ratio of 



V' 



100 



length 

*Mains for indirect radiation should have a rated capacity ap- 
proximating 66 per cent, of the values in this column. 



TABLE 34. 

Sizes of Hot-Water Branches and Risers. 

Open Tank System. 







Up Feed 




Down feed 


Pipe 








from attic 








diam. 


First 


Second 


Third 


Fourth 


not exceeding 


inches 


Floor 


Floor 


Floor 


Floor 


four floors 


1 


50 


65 


75 


m 


75 


m 


90 


110 


130 


145 


125 


11/2 


125 


160 


190 


215 


200 


2 


225 


300 


350 


375 


350 


21/2 


325 


425 


510 


580 


600 


3 


500 


600 


700 


800 


900 



Take first floor supply branches from top of main. Risers above first 
floor at 45°. 

TABLE 35. 

Hot-'U^ater Radiator Tappings. 

Open Tank System. 



Size of Radiator 


Supply and Return 


Up to 40 sq. ft. 

40 to 72 sq. ft. 

Above 72 sq. ft. 


1x1 
1% X 114 
11/2 X 11/2 



433 



TABLE 36. 
Honeywell System. Piije Sizes. 

The area of the main must equal or exceed slig-htly the 
combined area of the valves it is to supply. 



Riser Sizes and Square Feet of Eadiation. 




Pipe size, inches 


First Floor 


Second Floor 


Third Floor 


1/2 
% 
1 


Up to 30 
30 to 60 
60 to 100 


Up to 40 
40 to 100 
Over 100 


Up to 50 
50 to 125 
Over 125 



The valve on the radiator at the end of the main should generally be 
made one size larger than the list. 

TABLE 37. 

Gravity Hot-"Water Heating. Approximate Capacities of 

Mains and Risers for Range from 180 to 150 Oeg. Falir.$ 

Capacities (including- losses in transit) are in 1000 B. t. u. per hour 
and allow for average resistance of boilers, radiators and piping. For 
sq. ft. of radiating surface supplied (160 B. t. u. per sq. ft.), multiply 
the tabular figures by 6.25. 

MAINS. 







Diameter of main, in. 


Is 


IV4 


IV2 


2 


2Vf. 


3 


3% 


4 


4% 


5 


6 


7 


8 


C <s 


























StH 


w*" 


























^ 


Capacity in 1000 B. t. u. 


TOO 


7 


1,5 


22 


40 


60 


98 


133 


188 


240 


315 


480 


675 


900 


200 


8 


12.5 


18 


32 


50 


82' 


114 


157 


206 


270 


415 


590 


800 


300 


9 


11 


16 


29 


45 


75 


106 


144 


190 


250 


.385 


550 


740 


400 


10 


10 


15 


27 


42 


70 


100 


135 


180 


238 


367 


520 


700 



RISERS. 





Diameter of riser, in. 


ii 


Diameter of riser, in. 


ii 

3 


% 


1 


11/4 11/2 


2 21/2 


1/2 


% 


1 


m 


11/2 


2 


m 


Capacity in 1000 B. t. u. 


Capacity in 1000 B. t. u. 


10 

15 

20 

2'5 


4.0 
5.0 
5.8 
6.4 


7.5 
9.2 
10.6 
11.8 


15.0 
18.7 
21.7 
24.2 


22.0 
27.4 
31.8 
35.5 


42 
52 
60 
67 


67 
82 
95 
106 


30 
40 
50 
60 


3.4 
4.0 
4.5 
4.9 


7.1 

8.2 
9.2 
10.1 


13.1 
15.2 
17.0 
18.5 


m 

31 
35 
38 


38 
45 
51 
56 


74 

86 

97 

107 



* The length and mean height above boiler are those of the circuit for 
the most distant radiator in lowest location. 

t The mean height above boiler is that of the circuit in question. This 
table is for a circuit 200 ft. long. For other lengths allow about in pro- 
portion as given above for mains. 

X Marks— M. E. Handbook. 

434 



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■^Me0C>J>-t-3i-^3i 

a)OcoLS>t~oi(M054> 

i-lt-lt-li-li-<(MC<lCO 

OlCSiSOiMCoCiOOfOlft 

Oii-<-<*iA00i-i-*q2Oa 
rHt-li-li-ICv](MC0CO 

iAajcoij^oioioooLO 
(^^(^ql-fot-cooOt-oi 

C>lMlOJ>01<NmC3-<* 






CO CO in 1-1 O o ( 

rH 10 00 ^ ?0 00 1 
(M rf t^ O CO CD I 
t-l i-l 1-1 (M <N <M I 



i^LOCOi£cO'3ii-<& 
LQ(Noir3002i-H^io 
MC0O<MC001-^c0c0 
i-(i-l(M(MC<l(MCO-*llA 



cOtri— lc60LQ-*'<iii 

iraoococoo-*OiOj 

I— Il-I(MC<ICOCOCOIOI 



C3©OO^t-lASO 
i-ltN(MC0C0-*-^COJ> 



■*C>OC>r-l<MOiCO£ 

i-iinooi-i&coTiit 

t~5"lQlA(MOJ00t-£ 
(MCO^-^lOLACOOOi 



TABLE 40. 
Sizes for Steam Supply and Return liines.f 



Pipe Sizes 



Supply mains, all .systems; 

downfeed risers, all systems. 
Upfeed risers, one^pipe system- 
Dry return lines, two-pipe and 

vapor systems 

Wet return lines 

Vacuum return lines 



50 



50 



iy4 



150 300 
2000 3800 
800 1500 



IVa 



175 
lOO 

900 
600O 
3000 



350 

20O 

2000 
13O0O 
6000 



21/2 



600 
300 

3800 
23000 
lOOOO 



1000 
500 

6000 
370O0 
18000 



31/2 



1500 

700 

10000 
5500O 
30OO0 



Pipe Sizes 


4 


5 


6 


8 


10 


12 


14 


16 


Supply mains, all systems: 

downfeed risers, all systems.. 
Upfeed risers,* one-pipe system 


2000 
800 

130OO 
7800O 
40O00 


3800 
1300 

23000 


6000 

180O 

37000 


130OO 

3000 

78000 


23000 


35000 


5500O 


78000 


Dry return lines, two-pipe and 










Wet return lines 












65000 






















~ 







Which carry condensation from radiators. 

TABLE 41. 
Sizes of Radiator Connections. 



One-pipe radiators 


Two-pipe radiators 


Size of 


Radiator 


Hori- 


Size of 


Size of 


Size of 


Radiator, 


connec- 


zontal 


Radiator, 


supply con- 


return con- 


square feet 


tion 


branch 


square feet 


nection 


nection 


20 




1 


48 


1 


% 


24 




IV4 


m 


IV4 


1 


40 


m 


11/4 


over 96 


11/2 


IV4 


60 


11/4 


11/2 








80 


IV2 


11/2 








100 


11/2 


2 








200 


2 


2 









t Allen and Walker. 



437 



^ .2 



a; 


rt 
rt 







fl 


rt 






^ 


fai) 


<D 


fl 


<i) 




«H 


^ 


o 
o 


o 


tH 


o 






rC! 




o 


a; 


crt 


^ 


<D 


■*-' 


rl 


bJD 




fi 






peeq jo ssot[ 


.296 
.611 
1.027 
1.54 
2.15 
2.85 




82.0 
48.1 
64.1 
80.2 
96.2 
112.0 



^99j m 
P'Baq JO s'sot; 



9^niiini 
jad q.89j biqno 



q.98j ui 
pBeq JO ssot: 



i9d ^99j biqno 



^9aj UI 
pB9q JO ssot; 



a^nuini 
i9d :^99j biqn,o 



Ct99J ni 
pB9q JO ssoq; 



i9d ^99j biquo 



^99j nt 
p'B9q JO s'soq; 



9:^mitui 
i9d ^99j btquo 



^99J UI 

pB9q JO ssoq; 



9:jnutui 
i9d ^99j biqno 



^99J UI 
pB9q JO SS01 



.taaii NI iLLB30T[3A 



<3i OOi- O 

T-I (M oj >A LO CO 

T*i o 00 c> e<i -* 



so O i-H t- ■ 



ic eo T-i Oi J> -* 
toi5i>|cop(y 



) C> CO QD 

i d d CO 



CO lO t~ Si tH C<! 



■<*l -^ lo 

m' CO T)H 



^ i^ Oi c<i ■>* aO 



a^ C:> C>_ CO t~ 
r-< l^j CO ■* Lft 



I 00 Se-1 



in 00 i-H ■^J> P 



I JM '^lAt- 



lM CO LO to t-- Oi 



CO -* e> 

rH rtH i-H 
T-H d -^ 



i> i-H in 

I-H CO -* 

coco r-5 



c<i "* 00 I 



o o o 

(M CO ■* 



o oo 
in CO t^ 



liii 



Oi in O i- r-i •<* 



N 00 -* O CO M 

(M CO •* in ^i^ 



gg: 



t-cO M O «0 
■^ p tH t- t- CO 
iH Co LO J^- o ■* 



iH r-1 C<1 CO CO ■ 



Ci Ci i:- rH Oi 
CO ;*Q0 ® <M i 

1-1 CO m 00 c-q ' 



ill! 



T-l 1-1 rH IM (M 



CO ^i> (N 

.-( •* -^ <M CO t' 
C<1 •* I> r-( in O 



gx^Sg^g^ 



■^ ■* CO 

CO ^ rH 1:^ (M CM 

e<i in Oi CO 02 in 



o o c> o o o 

M CO Tji lA CO* t^ 



TABLE 43. 

Comparative Sizes of Steam Mains and Returns for Gravity 

and Mechanical Vacuum Systems. 



Size of 

supply 

pipe 


Size of return 


Size of 

supply 

pipe 


Size of return 


Gravity 


Vacuum 


Gravity 


Vacuum 


% 

1 

iy2 

2 
3 

3y2 


% 
% 
1 

iy2 

2 
2 

2y2 


y2 
y2 
y2 

% 
% 
1 

m 
ly* 


4 

4y2 

5 

6 

8 
10 
12 
14 


2y2 

3y2 

4y2 

6 
6 

7 


iy2 
iy2 

2 

2y2 
3y2 

4 

4y2 

5 



Note. — For short runs of piping where the friction is not a serious 
matter the above table will work out satisfactorily. These sizes are 
only approximate and should be used with caution. 



TABLE 44. 
Expansion Tanks — Dimensions and Capacities. =* 



Size in inches 


Capacity gallons 


Sq. ft. of radiation 


9x20 


5y2 


150 


10x20 


8 


2.50 


12x20 


10 


3.50 


12x24 


12 


450 


12x30 


1.5 


550 


12x36 


18 


650 


14x30 


20 


700 


14x36 


24 


850 


16x30 


26 


900 


16x36 


32 


1250 


16x48 


42 


1750 


18x60 


66 


27.50 


20x60 


82 


4.500 


22x60 


100 


6000 


24x60 


122 


7500 



'The Model Boiler Manual. 



431 



TABLE 45. 
Sizes of Flanged. Fittings. 





All fittings and 1 




flanges 










<a 
































(D 




;-i 




tc 


^ 






•3 






fl 








.9 
a 


03 
O 


o 


i2 


1 
o 


m 


'" 




CO 


o 




o 


CO 

<11 


s 




O 




O 


O. 


03 


J3 


O 


03 


^ 


PM 


tt 


H 


^ 


5 


CO 



ir§{2ib9 



& 



hcw 




elbow 



45° 
elbow 






t9 



Long 
turn 
elbow 



Tee 



Oross 






to 



Sb 



Lateral 



to 



9 


H 


8 


7% 


% 


61/2 


11 


1 


8 


9% 


% 


8 


13% 


1% 


8 


11% 


% 


9 


IG 


li% 


12 


141/4 


78 


11 


19 


IV4 


12 


17 


% 


12 


21 


1% 


14 


18% 


1 


14 


23% 


It'h 


16 


2IV4 


1 


15 


27% 


m 


20' 


25 


1% 


18 


•62 


m 


20 


291/2 


1% 


22 



4 
5 
6 

7 

71/2 
71/2 
8 

91/2 
11 



6I/2 

8 

9 
11 
12 
14 
15 
18 



12 

141/2 

171/2 

201/2 

241/2 

2!7 

30 

35 

401/2 



SV2 

41/2 

5 

51/2 

6 

6I/2 



TABLE 46. 
Dimensions of Dills and Tees for Wrought Iron Pipe. 



ii>\\ur E 




- 1 


"_ 


" 


1 

T 


d 

D ► 


--D 



Size 


E 


R 


D 


d 


t 


L 


T 


i/s 


% 


i^^ 


it 


T% 


1% 


1-1/4 


% 


1/4 


% 


% 


1- 


% 


A 


1-1/2 


% 


% 


Vs 


% 


1-1/8 


78 


1/4 


1-% 


78 


1/2 


1-1/8 


78 


1-1/4 




1/4 


2-1/4 


1-1/8 


% 


1-% 


1-iV 


1-1% 


1-1% 


1% 


2-% 


1-% 


1- 


1-T^6 


1-1/4 


i-ys 


1-% 


1% 


3-1/8 


1-1% 


1-1/4 


i-ys 


1-1/2 


2-y4 


2- 


1% 


3-% 


1-78 


1-1/2 


9_ 


1-% 


2-1/2 


2-1/4 


% 


4- 


2- 


2- 


2-% 


2-1/8 


3-% 


2-78 


. % 


^% 


2-% 


2-1/2 


2-78 


2-1/2 


4- 


3-1/2 


% 


5-% 


2-78 


3- 


3-% 


2-% 


4-% 


4- 


78 


^% 


3-% 


3-1/2 


3-% 


3-1/8 


5-1/4 


4-% 


78 


7-74 


•3-% 


4- 


4- 


3-% 


5-78 


5-74 


1- 


8- 


4- 


4-1/2 


4-% 


4- 


6-1/8 


&- 


1- 


8-% 


^% 


0- 


^% 


^1/8 


6-1/2 


6-78 


1-78 


9-1/2 


4-% 


6- 


5-1/4 


4-% 


8-1/2 


7-78 


1-1/8 


11- 


5-1/2 



440 



47. 
Loss of PresKSure in Pipes 100 Feet Long in Ounces per 
Square Inch when Delivering Air at the Velocities Given. 



TABLE 
Pressure in Pipes 100 



fl.9 








Diameter of pipe in inches 










1 


2 


3 


4 


6 


8 


10 


12 


14 


16 


18 


800 


0.100 


0.0.50 


0.033 


0.025 


0.017 


0.012 


0.010 


O.O08 


0.007 


0.006 


0.006 


40O 


0.178 


0.088 


0.059 


0.044 


0.0.30 


0.022 


0.018 


0.015 


0.013 


0.011 


0.010 


600 


0.400 


0.200 


0.133 


0.100 


0.067 


0.050 


0.040 


0.033 


0.029 


0.025 


0.022 


800 


0.711 


0.356 


0.237 


0.178 


0.119 


0.089 


0.071 


0.059 


0.051 


0.044 


0.040 


1000 


1.111 


0.5.56 


O..370 


0.278 


0.1&5 


0.139 


0.111 


O.092 


0.079 


0.069 


0.062 


1200 


1.600 


O.80O 


0.533 


O.40O 


0.267 


0.200 


0.160 


0.133 


0.114 


O.IOO 


0.089 


1500 


2.500 


1.2'50 


0.833 


0.625 


0.417 


0.312 


0.250 


0.208 


0.179 


0.156 


0.139 


1800 


3.600 


1.800 


1.20O 


0.900 


0.600 


0.4.50 


0.360 


0.300 


0.2.57 


0.225 


0.200 


2400 


6.400 


3.200 


2.133 


1.600 


1.067 


0.800 


0.640 


0.533 


0.457 


0.400 


0.3.56 




20 


24 


28 


32 


36 


40 


44 


48 


52 


56 


60 


300 


0.005 


0.004 


0.004 


O.0O3 


O.0O3 


0.002 


0.002 


0.002 


0.002 


0.0O2 


0.002 


400 


O.OOO 


0.007 


0.006 


0.006 


O.0O5 


0.004 


O.0O4 


O.0O4 


O.0O3 


0.003 


0.0O3 


600 


0.020 


0.017 


0.014 


0.012 


0.011 


0.010 


O.0O9 


0.008 


0.008 


0.007 


0.007 


800 


0.036 


0.029 


0.025 


0.022 


0.020 


0.018 


0.016 


0.015 


0.014 


0.013 


0.012 


1000 


0.0.56 


0.046 


0.040 


0.035 


0.0.31 


0.028 


0.025 


0.023 


0.021 


0.O20 


0.019 


1200 


O.OSO 


0.067 


0.057 


0.050 


0.044 


0.040 


0.030 


0.033 


0.031 


0.029 


0.027 


150O 


0.125 


0.104 


0.089 


0.078 


0.069 


0.062 


0.057 


0.052 


0.048 


0.045 


0.042 


1800 


0.180 


0.167 


0.129 


0.112 


0.100 


0.090 


0.082 


0.075 


0.069 


0.064 


0.060 


240O 


0.320 


0.313 


0.239 


0.200 


0.178 


0.160 


0.145 


0.133 


0.123 


0.119 


0.107 



Diagrams for Pipe Sizes and Friction Heads. 

To illustrate the use of the two following- diagrams, ap- 
ply to the pipe line, B, C, Art. 147. First, let I = 1500 feet, 
d = 8 inches and v = 5 feet per second. Trace along- the 
velocity line until it intersects the diameter line, then fol- 
low the ordinate to the top of the pag-e and find the friction 
head, 13 feet for 1000 foot run or 19.5 feet for the 1500 foot 
run. Second, let Q = 1.75 cubic feet per second and d = S 
inches. Trace to the left along- the horizontal line represent- 
ing- the volume of 1.75 cubic feet until it intersects the 
diameter line, then read up and find the same friction head 
as before. Third, let the allowable friction head for 1500 
feet of main be 19 feet, when Q = 1.75 cubic feet per second 
or when v = 5 feet per second. Reverse the process g-iven 
above and find an 8 inch pipe. 



441 



■a^op39 ^^d l3sj piffnp f^i [ &] 3^u\/)iP9i(r 



O OOOOoOO OOO Oif>o lOfMO 
CO tM CM — -^ "- 



)in ^ rocM CM - 



in (M O <» <o < CO 
o d d c> 




aNoo39 )iU i33j oiaao ni [-q] ibilvH^siQ 




443 



TABLE 48. 



Temperature*) 


foi 


Testing 


Direct 


Stea 


111 Radiation 


Plants.* 




Test 


Steam 


Steam pressure intended for 


zero 


weather 




condi- 


Tem- 
















g 


tion 


pera- 
































!3 




ture 


01b. 


lib. 


2 1b. 


31b. 


41b. 


51b. 


61b. 


71b. 


81b. 


91b. 


101b. 


03 
> 


10 in. 


192.0 


63.3 


62.3 




















O 


9 " 


194.5 


64.2 


63.2 


62.3 


















S 


8 " 


197.0 


65.0 


64.0 


63.0 


62.2 
















^ 

u 


7 " 


199.0 


65.6 


64.7 


63.7 


62.8 


62.0 














a 


6 " 


201.0 


66.3 


65.3 


64.3 


63.4 


62.6 


62.0 














5 " 


203.0 


67.0 


66.0 


65.0 


64.0 


63.3 


62.6 


61.9 










a 


4 " 


205.0 


67.6 


m.6 


65.6 


64.7 


63.9 


63.2 


62.5 


61.7 










3 " 


207.0 


68.3 


67.2 


66.2 


65.3 


64.5 


63.8 


63.1 


62.3 


61.7 






ij 


2 " 


208.5 


68.8 


67.7 


66.7 


65.7 


65.0 


64.2 


63.6 


62.8 


62.0 


61.5 




OQ 


1 " 


210.5 


69.4 


68.3 


67.5 


66.4 


65.6 


64.8 


64.2 


63.3 


62.6 


62.1 


61.5 


^ 

S 


lb. 


212.0 


70^0 


68.8 


67.8 


66.9 


66.1 


65.3 


64.6 


63.8 


63.1 


62.6 


62.0 


G 


1 " 


215.5 


71.2 


70.0 


69.0 


68.0 


67.2 


66.3 


65.8 


65.0 


64.2 


63.7 


63.0 


S 


2 li 


218.7 


72.1 


71.0 


70.0 


69.2 


68.2 


67.3 


66.7 


65.9 


65.1 


64.5 


64.0 


^ 


S " 


221.7 




72.0 


71.0 


70.0 


69.2 


68.3 


67.6 


66.7 


66.0 


65.4 


64.8 


- 


4 " 


224.5 






71.8 


70.8 


70.0 


69.2 


68.4 


67.5 


66.7 


66.2 


65.7 


S 


5 " 


227.2 








71.7 


70.8 


70.0 


69.2 


68.3 


67.6 


67.0 


66.3 


M 


6 " 


229.8 










71.7 


70.8 


70.0 


69.2 


68.4 


67.7 


67.2 


S 


7 " 


232.4 












71.7 


70.8 


70.0 


69.2 


m.6 


68.0 


P< 


8 " 


234.9 














71.7 


70.8 


70.0 




68.7 


1 

o 


g » 


237.3 
















71.5 


70.5 


7o!o 


69.3 


10 " 


239.4 


















71.3 


70.7 
.705 


70.0 




Factors 


.670 


.675 


.678 


.684 


.688 


.692 


.694 


.698 


.702 


.707 



The temperatures in this table are for a plant designed for 0° and 70". 

'Example. — It is desired to test a plant designed for 5 pounds gage 
pressure on a day when the outside temperature is 22 degrees. What 
should be the temperature in the rooms with steam at 3 pounds gage 
pressure? It will be noted in the vertical column marked 5 pounds that 
opposite the 3 pound pressure 68.3 degrees may be expected on a zero 
day. As the temperature was 22 degrees above we must add 22 times 
.692, or 15.2 degi'ees, thus making a total of 83.5 degrees, the tempera- 
ture which should exist indoors. 

* W. W. Macon. 



444 



S8 



Sg 



00 00 



O O 

o o 



I (M GO 



-* CO ■<*( rjf -^ 

in 5C lo '^ 



CO e>T Ci Tj< c-i 



CO ■* eo CO to 



Oi ooo 

(M 00 M CO 

^ co^ 



Oi M O 

■ CO 00 c-i 



O-.' CO o 

I 00 in CO 



o 8 

00 CO <IC r-H CC o 
CO I I-H C-1 

(M 6-^ 



o S 

I 00 «D I-H «o -* 

1 I 1-1 00 



llr? 



"'"S^ 



oooo I 

O i-l CO CM A rn . 



e^i o o 

TtHOOr-^ CO 



I^Lft? 






'$b«o 



CO CO 



00 CO ^ ^ 



CO CO V, 5.^ 

(M <o 



I Lft in o 



1%.%^^^ 



88 

l-H (M 



88 



p ^ r-f C 
« ^ ■* 



(M 00 O ift o 

1-. . oothco'V'*'^ 

i 00 00 (25 I I-H (-In 1-1 CO 



8^: 



L, ^ ^ ^ I 00 T^ CO f , 

I (M t- 00 !> I I-l r^ 1 

(M (M "^ 



J> in ^ -^ 



ui Ci S<i CO 
l> in ^ ^ 



o e-i i-i ( 

00 CO ■* 



000 



S^g^S 



10 CO O 
i> CO oi 



MOO 
1 1>^ lA t-^ 



'if CO O 
H--I CO 06 



in d; '» « 
Oi in 



O5^§0O 



CD CO Si "1* in m 



CO CO ?! "f in S 



§0S5 



CM Si (M *f 1 



looo«^^ 

CO ^-. ^ 



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a o G a d ^' 



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03 S3 
03 03 



03 
Oi o 



^ o 



; o o 



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o o'S 



^ 


43 a 


a 


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u 


a 1 










ft 


a 


% 
^ 


^ i 


aft 






03 


S 


2 


'^-.b 



2SS r 



o o 



■^^bh 



fi 02 cc ;*< fi 02 



00 s 



■53 'S o 
M W pH 



K+i o 

C oj Jj 



tH 03 +J 

03 > 03 

pq OS'S 

X2 d 



r 03 w 



§ S ® 

a • 

03 03 03 
^ jH C3 
03 "^ 



3 in-' 






C 03.^ 
o 'h te 

O C3 ^ 



O 5 S 



! 5 ^ S 6 






445 



TABLE 50. 

Percentage of Heat Transmitted by Various Pipe-Coverings, 

From Tests Made at Sil>ley College, Cornell University, 

and at Michigan University.* 

Relative amount 
Kind of covering- of heat 

transmitted 

Naked Pipe 100. 

Two layers asbestos paper, 1 in. hair felt, and canvas 

cover 15.2 

Two layers asbestos paper, 1 in. hair felt, canvas cover 

w^rapped with manilla paper 15. 

Two layers asbestos paper, 1 in. hair felt 17. 

Hair felt sectional covering, asbestos lined 18.6 

One thickness asbestos board 59.4 

Four thicknesses asbestos paper 50.3 

Two layers asbestos paper 77.7 

Wool felt, asbestos lined 23.1 

Wool felt with air spaces, asbestos lined 19.7 

Wool felt, plaster paris lined 25.9 

Asbestos molded, mixed with plaster paris 31.8 

Asbestos felted, pure long- fibre 20.1 

Asbestos and sponge 18.8 

Asbestos and wool felt 20.8 

Magnesia, molded, applied in plastic condition 22.4 

Magnesia, sectional 18.8 

Mineral wool, sectional 19.3 

Rock wool, fibrous 20.3 

Rock wool, felted 20.9 

Fossil meal, molded, % inch thick 29.7 

Pipe painted with black asphaltum , 105.5 

Pipe painted with light drab lead paint 108.7 

Glossy white paint 95.0 

♦Carpenter's H. and V. B. 

Note. — These tests agree remarkably w^ell with a series 
made by Prof. M. B. Cooley of Michigan University, and also 
with some made by G. M. Brill, Syracuse, N. Y., and reported 
in Transactions of the American Society of Mechanical En- 
gineers, Vol. XVI. 



446 



TABLE 51. 
Factors of Evaporation. 



Gage 


.3 


10 


20 


30 


50 


100 


125 


1.35 


150 


175 


pressure 






















Feed 






Factors of evaporation 


water 








212 


1.0O03 


1.0103 


1.0169 


1.0218 


1.0290 


1.0396 


1.0431 


1.0443 


1.0460 


1.0483 


200 


1.0127 


1.0227 


1.0293 


1.0343 


1.0414 


1.0520 


1.0555 


1.0.567 


1.0.584 


1.0608 


185 


1.0282 


1.0382 


1.0448 


1.0498 


1.0569 


1.0675 


1.0710 


1.0722 


1.07.39 


1.0763 


170 


1.0437 


1.0537 


1.0603 


1.0653 


1.0724 


1.0830 


1.0865 


1.0877 


1.0894 


1.0917 


155 


1.0.592 


1.0692 


1.0758 


1.0807 


1.0878 


1.0985 


1.1020 


1.1032 


1.1048 


1.1072 


140 


1.0715 


1.084G 


1.0912 


1.0062' 


1.1033 


1.1139 


1.1174 


1.1186 


1.1203 


1.1227 


125 


1.0901 


1.1001 


1.1067 


1.1116 


1.1187 


1.1293 


1.1328 


1.1341 


1.13.57 


1.1331 


no 


1.1055 


1.11.55 


1.1221 


1.1270 


1.1341 


1.1447 


I. urn 


1.1495 


1.1511 


1.1.535 


95 


1.1209 


1.1309 


1.1375 


1.1424 


1.1495 


1.1602 


1.1637 


1.1649 


1.1665 


1.1689 


80 


1.1363 


1.1463 


1.1529 


1.1.578 


l.m50 


1.1756 


1.1791 


1.1803 


1.1820 


1.1843 


65 


1.1517 


1.1617 


1.1683 


1.1733 


1.1804 


1.1910 


1.1945 


1.1957 


1.1974 


1.19m 


50 


1.1672 


1.1772 


1.1838 


1.1887 


1.19.58 


1.2064 


1.2090 


1.2112 


1.2128 


1.21.52 


35 


1.1827 


1.1927 


1.1993 


1.2042 


1.2113 


1.2219 


1.22.55 


1.2267 


l.'^^X^ 


1.2307 



TABLE 52. 

Per Cent, of Total Heat of Steam Saved per Degree Increase 

of Feed Water. 



Initial 




Gage pressure in boiler, lbs 


per sq. in. 














































of feed 





20 


40 


60 


80 


lOO 


120 


140 


160 


180 


32 


0872 


.0861 


0855 


.0851 


.0847 


.0844 


.0841 


.0839 


.0ec37 


.0835 


40 


0878 


.0867 


0861 


.08.56 


.0853 


.08.50 


.0847 


.0845 


.0843 


.0839 


50 


0686 


.0875 


0868 


.0864 


.0860 


.oa57 


.08.54 


.0852 


.08.50 


.0846 


60 


0894 


.0883 


0876 


.0«72 


.0867 


.0864 


.0862 


.08.59 


.0&56 


.0&53 


70 


0902 


.0890 


0884 


.0879 


.0875 


.0872 


.0869 


.0867 


.0864 


.0860 


80 


0910 


.0898 


0891 


.0887 


.0883 


.0®79 


.0877 


.0874 


.0872 


.0868 


lOO 


0927 


.0915 


0908 


.0903 


.0899 ' 


.0895 ' 


.0892 ■ 


.0890 


.0887 


.0883 


120 


0945 


.0932 


0925 


.0919 


.0915 


.0911 


.0908 


.0906 


.0903 


.0899 


140 


0963 


.0950 


0943 


.0937 


.0932 


.0929 


.0925 


.0923 


.0920 


.0916 


160 


0982 


.0968 


0961 


.0955 


.0950 


.0946 


.0943 


.0940 


.0937 


.0933 


180 


1002 


.0988 


0981 


.0973 


.0969 


.0965 


.0961 


.0958 


.0955 


.0951 


200 


1022 


.1008 


0999 


.0993 


.0988 


.0984 


.0980 


.0977 


.0974 


.0969 


220 _ 




.1029 


1019 


.1013 


.1008 


.1004 


.1000 


.0997 


.0994 


.0989 


240 _ 




.1050 


1041 


.1034 


.1029 


.1024 


.1020 


.1017 


.1014 


.1009 



Example.— Boiler pressure 120 lbs. gage, initial temperature of feed 
water 60 deg., heated to 210 deg. Then increase in temperature 150, 
times tabular figure, .0862, equals 12.93 per cent, saving. 



447 



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75.2 
86.0 
96.7 
107.5 
118.2 
129.0 
139.7 
150.5 
161.2 
172.0 


182.7 
193.5 
204.2 
215.0 
225.7 


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TABLE 54. 

Steam Consumption of Various Types of Non-Condensing,- 

Eng'ines.* (Approximate). 

Pounds per indicated horse-power hour. 













Com- 


Com- 


Com- 




Simple 


Simple 






pound 


pound 


pound 




throt- 


auto- 


Simple 


Simple 


four 


four 


four 


Horse- 


tling 


matic 


Corliss 


four 


valve and 


valve and 


valve and 


power 


lOOlbs. 


100 lbs. 


100 lbs. 


valve 


Corliss 


Corliss 


Corliss 




at 


initial 


initial 


lOOlbs. 


lOOlbs. 


125 lbs. 


150 lbs. 




throttle 






initial 


initial 


initial 


initial 


10 


52 














20 


50 


40.0 












30 


49 


39.0 












40 


48 


38.0 












50 


48 


38.0 


34.5 


35.0 








60 


47 


36.0 


32.5 


33.0 








70 


47 


35.0 


31.5 


32.0 








80 


46 


34.0 


30.5 


31.0 








90 


45 


33.0 


29.5 


30.0 








100 


45 


32.0 


28.5 


29.0 








150 


44 


31.5 


28.0 


28.5 


22.. 5-23 


21.. 5-22 


21-21.5 


20O 


43 


30.5 


27.0 


27.5 


22-22.5 


21-21.5 


20.5-21 


250 


43 


30.0 


26.5 


27.0 


22-22.5 


21-21.5 


20-20.5 


300 


42 


29.0 


25.5 


26.0 


22-22.5 


20.. 5-21 


20-20.5 


400 


41 


28.5 


25.0 


25.5 


21.5-22 


20-20.5 


19.5-20 


500 


41 


28.5 


25.0 


25.5 


20-21.5 


19.5-20 


19^19.5 



The foreg-oing- table was compiled principally from the records of a 
large number of actual tests of engines of various makes, under reason- 
ably favorable conditions. It is based upon the actual weight of con- 
densed exhaust steam. 

* Atlas Engine Works Catalog. 



449 



TABLE 55. 

Speeds, Capacities and Horse-Powers of "Green" Steel Plate 

Fans at Varying Pressures.* 



11 




.26 in. 


.87 in. 


1.3 in. 


1.7 in. 


2.2 in. 


2.6 in. 


Sm in. 


3.46 in. 


4.33 in. 


Pressures 




















%oz. 


V2 oz. 


%oz. 


loz. 


1% oz 


11/2 oz 


1% oz. 


2oz. 


21/2 oz. 




OU. FT. 


2249 


3176 


8891 


4498 


5029 


5513 


5956 


6372 


7135 


so 


R. P. M. 


830 


466 


571 


660 


738 


m& 


874 


935 


1047 




H. P. 


.286 


.811 


1.491 


2.298 


3.213 


4.227 


5.311 


6.515 


9.120 




CtJ. FT. 


3239 


4581 


5605 


6477 


7242 


7937 


8584 


9173 


10268 


so 


R. P. M. 


275^ 


389 


476 


550 


615 


674 


729 


779 


872 




H. P. 


.413 


1.170 


2.148 


3.311 


4.625 


6.086 


7.681 


9.375 


13.125 




OU. FT. 


4398 


6214 


7617 


8815 


9864 


10799 


11679 


12483 


13981 


42 


R. P.M. 


235 


332 


407 


471 


527 


577 


624 


667 


747 




H. P. 


.557 


1.576 


2.808 


5.473 


0.300 


8.287 


10.450 


12.750 


17.825 




CU. FT. 


5750 


8123 


9937 


11500 


12867 


14123 


15240 


16301 


18282 


48 


R. P. M. 


206 


291 


356 


412 


461 


506 


546 


584 


6.55 




H. P. 


.733 


2.076 


3.810 


5.880 


8.223 


10.832 


13.636 


16.670 


23.370 




CU. FT. 


7602 


10758 


13167 


15203 


17080 


18650 


20145 


21558 


24174 


54 


R. P. M. 


183 


259' 


317 


366 


410 


449 


485 


519 


582 




H. P. 


.970 


2.750 


5.047 


7.767 


10.880 


14.300 


18.017 


21.992 


30.896 




CU. FT. 


9715 


13718 


16780 


19429 


21725 


23786' 


25728 


27495 


307^ 


eo 


R. P. M. 


165 


233 


285' 


830 


869 


404 


4.37 


467 


523 




H. P. 


1.241 


3.506 


6.433 


9.932' 


13.882' 


18.280 


22.996 


28.077 


39.355 




CU. FT. 


12078 


17071 


20855 


24156 


26975 


29551 


32'047 


34221 


38247 


m 


R. P. M. 


150 


212 


259 


30O 


885 


367 


398 


425 


475 




H. P. 


1.542 


4.361 


7.996 


12.352 


17.238 


22.666 


28.675 


35.123 


48.895 




OU. FT. 


15608 


21942 


26918 


31108' 


34835 


38115 


41169 


44109 


49312 


72 


R. P. M. 


138 


194 


238 


275i 


308 


887 


364 


390 


486 




H. P. 


1.983 


5.601 


10.322 


15.881 


22.252 


29.223 


36.808 


45.043 


62.783 




CU. FT. 


20132 


2'8405 


34907 


40883 


45174 


49452 


53387 


57152 


63996 


84 


R. P. M. 


118 


166 


204 


236 


264 


289 


312 


334 


374 




H. P. 


2.581 


7.260 


13.887 


20.650 


28.875 


37.931 


47.775 


58.450 


81.812 




CU. FT. 


23008 


32614 


89762 


46016 


51601 


56515 


60083 


65227 


73045 


96 


R. P. M. 


108 


146 


178 


206 


231 


253 


273 


292 


327 




H. P. 


2.941 


8.337 


15.261 


23.531 


32.982 


43.348 


.54.511 


66.707 


93.380 




CU. FT. 


29260 


41027 


50568 


58519 


65198 


71559 


77284 


82690 


92549 


108 


R. P. M. 


92 


129 


159 


184 


205 


225 


243 


260 


291 




H. P. 


3.737 


10.488 


19.397 


30.060 


41.666 


54.871 


69.163 


84.556 


118.291 




CU. FT. 


36209 


51042 


62384 


71982 


8027O 


88559 


95539 


102083 


114298 


120 


R. P. M. 


83 


117 


143' 


165 


184 


208 


219 


234 


262 




H. P. 


4.628 


13.050 


23.925 


36.807 


51.307 


67.928 


85.495 


104.401 


146.116 




CU. FT. 


43560 


61565 


75504 


87120 


97575 


106868 


115680 


123711 


138231 


132 


R. P. M. 


75 


106 


130 


150 


168 


184 


199 


213 


238 




H. P. 


5.568 


15.730 


28.957 


44.550 


62.370 


82.096 


103.430 


126.521 


176.715 




CU. FT. 


52026 


73138 


89726 


103298 


116116 


127426 


137228 


147030 


164372 


144 


R. P. M. 


69 


97 


119 


137 


154 


169 


182 


195 


218 




H. P. 


6.65 


18.700 


34.411 


52.822 


74.221 


97.741 


122.802 


150.371 


210.133 



Manufacturer's Note.— The horse-power required to drive a fan will 
vary according' to the manner of application. The horse-powers given 
above are 25 per cent, greater than would be required under ideal condi- 
tions. 

* Condensed from the G. F. E. Co. Catalog. 



TABLE 56. 

Speeds, Capacities and Horse-Powers of "A. B. C." Steel 

Plate Fans at Varying Pressures.* 



1 


o 






V2" 


1" 


11/2" 


2" 


21/2" 


3" 


31/2" 


4" 




Static 


















^ 


i1 


press. 


















li 


















•^■B 






.29 


.58 


.87 


1.16 


1.44 


1.73 


2.02 


2.31 


^12; 


p. ^ 






oz. 


oz. 


oz. 


oz. 


oz. 


oz. 


oz. 


oz. 









P.M. 


3840 


5425 


6640 


7650 


8595 


9400 


10110 


10810 


50 


so 


R 


P.M. 


471 


665 


816 


945 


1060 


1150 


1250 


1330 






B 


H. P. 


.88 


2.48 


4.55 


7.00 


9.81 


12.85 


16.20 


19.75 









P.M. 


5475 


7740 


9460 


1090O 


12250 


1340O 


14410 


15420 


60 


86 


R. 


P.M. 


393 


555 


681 


786 


880 


961 


1040 


1110 






B. 


H. P. 


1.25 


3.53 


6.49 


9.94 


14.00 


18.35 


23.10 


28.10 






C. 


P. M. 


7100 


10020 


12280' 


14150 


15900 


17400 


18700 


20010 


70 


42 


R. 


P. M. 


336 


475 


583 


675 


755 


825 


890 


950 






B. 


H. P. 


1.62 


4.58 


8.35 


12.93 


18.19 


23.80 


29.90 


36.60 






C. 


P. M. 


8640 


122:00 


14950 


17200 


19350 


21150 


22800 


24350 


80 


48 


R. 


P. M. 


294 


416 


511 


590 


660 


722 


780 


832 






B. 


H. P. 


1.97 


5.57 


10.20 


15.71 


22.10 


28.90 


36.50 


44.50 






O. 


P. M. 


11000 


15540 


190O0 


21900 


246001 


26950 


2900O 


81000 


90 


54 


R. 


P. M. 


262 


370 


454 


525 


587 


641 


693 


740 






B. 


H. P. 


2.52 


7.08 


13.00 


20.00 


28.10 


36.85 


46.40 


56.50. 






C. 


P. M. 


14050 


19850 


24300 


280OO' 


81450 


3440O 


37000 


39600 


100 


00 


R. 


P. M. 


236 


333 


400 


473 


529 


578 


625 


665 






B. 


H. P. 


3.21 


9.05 


16.65 


25.60 


35.95 


47.10 


59.10 


72.30 






C. 


P. M. 


16600 


2350O 


2880O 


33100 


37200 


4O70O 


4380O 


46900 


110 


m 


R. 


P. M. 


214 


303 


371 


430 


480 


525 


568 


605 






B. 


H. P. 


3.80 


10.75 


19.70 


30.25 


42.50 


55.60 


70.00 


85.60 






G. 


P.M. 


20300 


2870O 


35100 


40500 


45500 


4970O 


53500 


57300 


120 


72 


R. 


P. M. 


196 


278 


340 


394 


440 


481 


520 


555 






B. 


H. P. 


4.64 


13.10 


24.00 


87.00 


.52.00 


68.00 


85.50 


104.50 






C. 


P. M. 


27400 


38700 


4Y400 


5450O 


6130O 


670I0O 


72200 


77250 


140 


84 


R. 


P.M. 


168 


238 


292 


337 


378 


413 


445 


475 






B. 


H. P. 


6.25 


17.75 


32'. 40 


49.80 


70.00' 


91.70 


115.20 


140.9 






C. 


P. M. 


34500 


48900 


59800 


68900 


7730O 


8450O 


91000 


97500 


160 


m 


R. 


P.M. 


147 


208 


256 


296 


331 


362 


390 


416 






B. 


H. P. 


7.88 


22.30 


41.00 


62.90 


88.40 


115.5 


145.4 


178.0 






O. 


P. M. 


42600 


60300 


73800 


85000- 


95500 


104300' 


112500 


120000 


180 


108 


R. 


P. M. 


131 


185 


227 


262 


298 


320 


346 


369 






B. 


H. P. 


9.75 


27.55 


50.50 


77.60 


109.0 


143.0 


180.0 


219.0 






C. 


P. M. 


51600 


73O0O 


89400 


108000 


L1570O 


126500 


136100 


145800 


20O 


120 


R. 


P. M. 


118 


166 


204 


236 


264 


289 


312 


332 






B. 


H. P. 


11.8 


33.30 


61.20 


93.50 


132.1 


173.0 


217.50 


266.0 






G. 


P.M. 


61400 


86800 


106000 


122200' 


137400 


150200 


162000 


173000 


220 


132 


R. 


P. M. 


107 


151 


185 


214 


240 


262' 


283 


302 






B. 


H. P. 


14.0 


39.60 


72.50 


111.. 50 


1.57.0 


206.0 


259.0 


316.0 






O. 


P. M. 


7200O 


101800 


124500 


143500 


161000 


176000 


189500 


203000 


240 


144 


R. 


P.M. 


98 


139 


170 


197 


220 


241 


260 


377 






B. 


H. P. 


16.5 


46.50 


85.00 


131.00 


184.0 


241.0 


303.0 


370.5 



Manufacturer's Note. — Any of the above fans, when running- at the 
speed and pressure indicated, wiU deliver the volume of air and require 
no more power than given in the table. 

Allowances must be made for the inefficiency of the motive power 
and for transmission losses between motive power and the fan. 

* Condensed from the A. B. O. Co. Catalog. 



TABLE 57. 
Speeds, Capacities and Horse-Powers of "Sirocco" Fans at 
Varying Pressures.* 



1 


o ! 




% 


1 


m 


11/2 


2 


21/2 


3 


3V2 


4 








in. 


in. 


in. 


in. 


in. 


in. 


in. 


in. 


in. 


i'^ 


Pressures 






































.S-G 






.43 


.58 


.72 


.87 


1.16 


1.44 


1.73 


2.02 


2.31 


5 ^1 
1 




oz. 


oz. 


oz. 


oz. 


oz. 


oz. 


oz. 


oz. 


oz. 






C. 


F. M. 


4260 


4920 


5500 


6020 


6945 


7770 


8520 


9200 


9840 


4 


24 


R. 


P. M. 


391 


453 


505 


564 




714 


783 


840 


905 






B. 


H. P. 


.879 


1.348 


1.89 


2.475 


3.8 


5.32 


7.00 


8.825 


10.77 






G. 


P.M. 


6650 


7690 


8600 


9416 


10870 


12150 


13320 


14380 


15380 


5 


30 


R. 


P.M. 


313 


362 


403 


443 


512 


571 


625 


076 


724 






B. 


H. P. 


1.37 


2.105 


2.90 


3.868 


5.95 


8.315 


10.94 


13.80 


10.85 






G. 


F. M. 


9580 


1106O 


12350 


13540 


15630 


17470 


19150 


20080 


22150 


6 


38 


R. 


P. M. 


260 


302 


338 


309 


427 


477 


523 


565 


004 






B. 


H. P. 


1.975 


3.03 


4.25 


5.563 


8.56 


11.90 


15.72 


19.85 


24.23 






C. 


P.M. 


13O50 


15070 


1680O 


18425 


21260' 


2380O 


2610O 


2820O 


30140 


7 


42 


R. 


P. M. 


223 


259 


288 


316 


366 


408 


447 


483 


517 






B. 


H. P. 


2.60 


4.120 


5.78 


7.565 


11.60 


10.28 


21.43 


27.06 


33 






C. 


P.M. 


170OO 


19700 


22000 


2410O 


27820 


31100 


34080 


308OO 


39370 


8 


48 


R. 


P.M. 


196 


226 


252 


277 


320 


358 


392 


424 


453 






B. 


H. P. 


3.51 


5.39 


7.58 


9.9 


15.22 


21.30 


28.0 


35.3 


43.15 


• 




C. 


P. M. 


21500 


24860 


27800 


30440 


35140 


39300' 


4310O 


40000 


49800 


9 


54 


R. 


P. M. 


174 


201 


224 


240 


2'85 


.317 


348 


370 


402 






B. 


H. P. 


4.43 


6.81 


9.57 


12.52 


19.23 


26.94 


35.38 


44.70 


54.5 






O. 


P. M. 


26500 


30750 


34300 


37050 


43400 


48570 


53220 


57500 


61500 


10 


60 


R. 


P.M. 


156 


181 


202 


222 


256 


286 


313 


338 


302 






B. 


H. P. 


5.46 


8.42 


11.8 


15.47 


23.77 


33.23 


43.72 


55.2 


07.4 






0^ 


P. M. 


3220O 


37200 


4150O 


45530 


52550 


58830 


64450 


69030 


74400 


11 


60 


R. 


P.M. 


142 


105 


184 


202 


233 


200 


285 


308 


329 






B. 


H. P. 


6.65 


10.18 


14.3 


18.72 


28.77 


40.24 


52.9 


00.85 


81.5 






C. 


P. M. 


3830O 


44240 


4940O 


54130 


6250O 


09900 


70000 


82800 


88500 


12 72 


R. 


P. M. 


130 


151 


108 


185 


214 


238 


261 


282 


302 




B. 


H. P. 


7.9 


12.11 


17 


22.25 


34.2 


47.85 


63 


79.5 


97 




O. 


P.M. 


45000 


52000 


5810O 


68000 


7350O 


8210O 


90000 


97300 


104000 


13 78 


R. 


P.M. 


120 


140 


155 


171 


197 


220 


241 


201 


279 




B. 


H. P. 


9.28 


14.22 


20 


20.10 


40.22 


56.2 


74 


93.35 


113.9 






G. 


P. M. 


52100 


60200 


073OO 


73700 


8500O 


95000 


104200 


112700 


120400 


14 


84 


R. 


P. M. 


112 


1.30 


144 


158 


183 


204 


224 


242 


259 






B. 


H. P. 


10.75 


16.49 


23.2 


30.3 


46.6 


65 


85.6 


109 


132 






C. 


P.M. 


59900 


69230 


77500 


84700 


9780O 


100200 


119800 


129600 


138500 


15 


90 


R. 


P. M. 


Wi 


121 


135 


148 


171 


191 


209 


226 


242 






B. 


H. P. 


12.34 


18.93 


20.6 


34.8 


53.55 


74.9 


98.5 


124.2 


151.7 






O. 


P. M. 


67950 


78430 


81800' 


96140 


114300 


124500 


130000 


147000 


157300 


16 


96 


R. 


P. M. 


98 


114 


120 


139 


100 


178 


196 


211 


220 






B. 


H. P. 


13.98 


21.5 


30.2 


39.6 


63 


85.7 


112 


142 


173 



Condensed from A. B. G. Co. Catalog. 



452 



APPENDIX II, 



References used Chiefly in Refrigeration 
and Ice Production 



TABLE 58, 
Freezing Mixtures.* 



Names and proportions of ingredients 
in parts 



Reduction of 


temp. 


ieg. F. 


Prom 


To 




— 5 




—12 




—25 


+S2 


—40 




— 5 


+32 


—23 


+32 


—27 


+32 


—30 


+32 


—51 


+50 


+ 4 


+50 


+ 4 


+50 


+ 4 


+50 


+ 3 


+50 


— 3 


+50 


— 7 


+50 


—10 


+50 


—12 


+50 


—14 



Total 
Reduc- 
tion of 
temp, 
deg-. P. 



Snow or pounded ice 2; sodium chloride 1 

Snow 5; sodiimi chloride 2; ammonium chloride 1 
Snow 12; sodium chloride 5; ammonium nitrate 5 

Snow 8; caleiura chloride 5 

Snow 2; sodium chloride 1 

Snow 3; dilute sulphuric acid 2 

Snow 3; hydrochloric acid 5 

Snow 7; dilute nitric acid 4 

Snow 3; potassium 4 

Ammonium chloride 5; potassium nitrate 5; 

water 16 

Ammonium nitrate 1; water 1 

Ammonium chloride 5; potassium nitrate 5; 

sodium sulphate 8; water 16 

Sodium sulphate 5; dil. sulphuric acid 4 

Sodium nitrate 3; dil. nitric acid 2 

Amonium nitrate 1; sodium carbonate 1; 

water 1 

Sodium sulphate 6; ammonium chloride 4; 

potassium nitrate 2; dil. nitric acid 4 

Sodium phosphate 9; dil. nitric acid 4 

Sodium sulphate 6; ammonium nitrate 5; 

dil. nitric acid 4 



TABLE 59. 
Properties of Saturated Aminonia.i 





Pressure 




Vol. of 


Vol. of 


Wt. of 


Temp. 


absolute 


Heat of 


vapor 


liquid 


vapor 


deg. F. 


lbs. per 


vaporization 


per lb. 


per lb . 


lbs. per 




sq. m. 




cu. ft. 


cu. ft. 


cu. ft. 


—40 


10.69 


579.67 


24.38 


.0234 


.0411 


-^5 


12.31 


576.69 


21.21 


.0236 


.0471 


—30 


14.13 


573.69 


18.67 


.0237 


.0535 


—25 


16.17 


570.68 


16.42 


.a238 


.0609 


—20 


18.45 


567.67 


14.48 


.0240 


.0690 


—15 


20.99 


564.64 


12.81 


.0242 


.0775 


—10 


23.77 


561.61 


11.36 


.0243 


.0880 


— 5 


27.57 


558.56 


9.89 


.0244 


.1011 


+ 


30.37 


555.50 


9.14 


.0246 


.1094 


+ 5 


34.17 


552.43 


8.04 


.0247 


.1243 


+10 


38.55 


549.35 


7.20 


.0249 


.1381 


+20 


47.95 


543.15 


5.82 


.0252 


.1721 


+30 


59.41 


536.92 


4.73 


.0254 


.2111 


+40 


73.00 


530.63 


3.88 


.0257 


.2577 


+50 


88.96 


524.30 


3.21 


.02601 


.3115 


+60 


107.60 


517.93 


2.67 


.0265 


.3745 


+70 


129.21 


511.52 


2.24 


.0268 


.4664 


+80 


154.11 


504.66 


1.89 


.0272 


.5291 


+90 


182.80 


498.11 


1.61 


.0274 


.6211 


+100 


215.14 


491.50 


1.36 


.0279 


.7353 



*Tayler. Pocket Book of Refrigeration. 

tWood — Thermodynamics, Heat Motors and Refrigerating Machines. 

454 



TABLE 60. 



Solubility of Ammonia in "Water at Different Temperatures 

and Pressures. (Sims).* 

1 lb. of water (also unit volume) absorbs the following 
quantities of ammonia. 



Absolute 


32° 


F. 


68" 


F. 


104° 


F. 


212° 


F. 


pressure 

in lbs. 

per 


































sq. m. 


Lbs. 


Vols. 


Lbs. 


Vols. 


Lbs. 


Vols. 


Grms. 


Vols. 


14.67 


0.899 


1180 


0.518 


683 


0.838 


443 


0.074 


97 


15.44 


0.937 


1231 


0..535 


703 


0..349 


4.58 


0.078 


102 


16.41 


0.980 


1287 


0.5.56 


730 


0.363 


476 


0.083 


109 


17.37 


L029 


13.51 


0..574 


754 


0.378 


496 


0.088 


115 


18.34 


1.077 


1414 


0..594 


781 


0.391 


513 


0.092 


■ 120 


19.30 


1.126 


1478 


0.613 


805 


0.404 


531 


0.096 


126 


20.27 


1.177 


1546 


0.632 


830 


0.414 


543 


0.101 


132 


21.23 


1.236 


1615 


0.651 


855 


0.425 


558 


0.106 


139 


22.19 


1.283 


1685 


0.669 


878 


0.434 


570 


0.110 


140 


23.16 


1.336 


1754 


0.685 


894 


0.445 


584 


0.115 


151 


24.13 


1.388 


1823 


0.704 


924 


0.454 


596 


0.120 


157 


25.09 


1.442 


1894 


0.722 


948 


0.463 


609 


0.125 


164 


26.06 


1.496 


1965 


0.741 


973 


0.472 


619 


0.130 


170 


27.02 


1.549 


2034 


0.761 


999 


0.479 


629 


0.135 


177 


27.99 


1.603 


2105 


0.780 


1023 


0.486 


638 






28.95 


1.656 


2175 


0.801 


1052 


0.493 


647 






30.88 


1.758 


2309 


0.842 


1106 


0.511 


671 






32.81 


1.861 


2444 


0.881 


11.57 


0..530 


696 






34.74 


1.966 


2582 


0.919 


1207 


0.547 


718 






36.67 


2.070 


2718 


0.955 


12.54 


0.565 


742 







TABLE 61. 
Strength of Ammonia Liquor. 



Degrees 


Specific 


Percent- 


Degrees 


Specific 


Percent- 


Baume 


gravity 


age 


Baume 


gravity 


age 


10 


1.0000 


0.0 


20 


0.93.33 


17.4 


11 


0.9929 


1.8 


21 


0.9271 


19.4 


12 


0.98.59 


3.3 


22 


0.9210 


21.4 


13 


0.9790 


5.0 


23 


0.9150 


23.4 


14 


0.9722 


6.7 


24 


0.9090 


25.3 


15 


0.9655 


8.4 


25 


0.9032 


27.7 


16 


0.9589 


10.0 


26(a) 


0.8974 


30.1 


17 


0.9523 


11.9 


27 


0.8917 


32.5 


18 


0.9459 


13.7 


28 


0.8860 


35.2 


19 


0.9396 


15.5 


29 


0.8805 





Note. — Sp. gr. of pure anhydrous ammonia = .623. 
(a) Known to the trade as "29i/^ per cent." 
*Tayler. Pocket-Book of Refrigeration. 



455 



TABLE 62. 
Properties of Saturated Sulphur Dioxide. 



(Ledoux). 





Absolute 










Temp, of 


pressure 


Total heat 


Latent heat 


Heat of 


Density of 


ebiallition 


lbs. per 


from 


of vapor- 


liquid 


vapor 


deg. F. 


sq. in. 


32 deg. P. 


ization 


from 


wt. per 




P -^ 144 






32 deg. P. 


cu. ft. 


—22 


5.56 


157.43 


176.99 


-19.56 


.076 


—13 


7.23 


158.64 


174.95 


—16.30 


.097 


— 4 


9.27 


159.84 


172.89 


—13.05 


.123 ■ 


5 


11.76 


161.03 


170.82 


— 9.79 


.153 


14 


14.74 


162.20 


168.73 


— 6.53 


.190 


23 


18.31 


163.36 


166.63 


— 3.27 


.232 


32 


22.53 


164.. 51 


164.51 


o.oo 


.282 


41 


27.48 


165.65 


162.38 


3.27 


.340 


50 


33.25 


166.78 


160.23 


6.. 55 


.407 


59 


39.93 


167.90 


158.07 


9.83 


.483 


68 


47.61 


168.99 


155.89 


13.11 


.570 


77 


56.39 


170.09 


153.70 


16.39 


.669 


86 


66.36 


171.17 


151.49 


19.69 


.780 


95 


77.64 


172.24 


149.26 


22.98 


.906 


104 


90.31 


173.30 


147.02 


26.28 


1.046 



TABLE 63. 
Properties of Saturated Carbon Dioxide. 





Absolute 










Temp, of 


pressure 


Total heat 


Latent heat 


Heat of 


Density of 


ebullition 


in lbs. 


from 


of vapor- 


liquid 


vapor or 


deg. P. 


per 


32 deg. P. 


ization 


from 


wt. per 




sq. m. 






32 deg. P. 


cu. ft. 


22 


210 


98.35 


136.15 


—37.80 


2.321 


—13 


249 


99.14 


131.65 


—32.51 


2.759 


— 4 


292 


99.88 


126.79 


—26.91 


3.265 


5 


342 


100.58 


121.50 


—20.92 


3.853 


14 


396 


101.21 


115.70 


—14.49 


4.535 


23 


457 


101.81 


109.37 


— 7.56 


5.331 


32 


525 


102.35 


102.35 


0.00 


6.265 


41 


599 


102.84 


94.52 


8.32 


7.374 


50 


680 


103.24 


85.64 


17.60 


8.708 


59 


768 


103.59 


75.37 


28.22 


10.356 


68 


864 


103.84 


62.98 


40.86 


12.480 


77 


968 


103.95 


46.89 


57.06 


15.475 


86 


1080 


103.72 


19.28 


84.44 


21.519 



* Kents' M. E. Pocket-Book. 
tl. C. S. Pamphlet 1238 B. 



TABLE 64. 

Pressures and Boiling Points of Liquids Available for Use 

in Refrigerating- Machines.* 



Tempera- 








ture of 




Pressure of vapor 




ebullition 




Pounds per square inch absolute 


deg. F. 


Sulphur 


Ammonia 


Carbon 


Pictet 




dioxide 




dioxide 


fluid 


-^0 




10.22 






—31 




13.23 






—22 


5.56 


16.95 






-13 


7.23 


21.51 


251.6 




— i 


9.27 


27.04 


292.9 


13.5 


5 


11.76 


33.67 


340.1 


16.2 


14 


14.75 


41.58 


393.4 


19.3 


23 


18.31 


50.91 


453.4 


22.9 


32 


22.53 


61.85 


520.4 


26.9 


41 


27.48 


74.55 


.594.8 


31.2 


50 


33.26 


89.21 


676.9 


36.2 


59 


39.9S 


105.99 


766.9 


41.7 


68 


47.62 


125.08 


864.9 


48.1 


77 


56.39 


146.64 


971.1 


55.6 


86 


66.37 


170.83 


1085.6 


64.1 


95 


77.64 


197.83 


1207.9 


73.2 


104 


90.32 


227.76 


1338.2 


82.9 



TABLE 65. 
Table of Calcium Brine Solution.f 



Deg. 


Per cent. 












Baume 


calcium 


Lbs. per 


Specific Si 


)ecific 


Freezing 


Amm. 


60 deg. 


by 


cu. ft. 


gravity t 


leat 


point 


gage 


P. 


weight 


solution 






deg. F. 


pressure 





0.000 


0.0 


l.OOO 1 


000 


32.00 


47.31 


2 


1.886 


. 2.5 


1.014 


988 


30.33 


45.14 


4 


3.772 


5.0 


1.028 


972 


28.58 


43.00 


6 


5.658 


7.5 


1.043 


955 


27.05 


41.17 


8 


7.544 


10.0 


1.058 


936 


25.52 


39.35 


10 


9.430 


12.5 


1.074 


911 


22.80 


36.30 


12 


11.316 


15.0 


1.090 


890" 


19.70 


32.93 


14 


13.202 


17.5 


1.107 


878 


16.61 


29.63 


16 


15.088 


20.0 


1.124 


866 


13.67 


27.04 


18 


16.974 


22.5 


1.142 


854 


10.00 


23.85 


20 


18.860 


25.0 


1.160 


844 


4.60 


19.43 


22 


20.746 


27.5 


1.179 


834 


— 1.40 


14.70 


24 


22.632 


30.0 


1.198 


817 


— 8.60 


9.96 


26 


24.518 


32.5 


1.218 


799 


—17.10 


5.22 


28 


26.404 


35.0 


1.239 


778 


—27.00 


.65 


30 


28.290 


37.5 


1.261 


757 


-^9.20 


8.5" vac. 


32 


30.176 


40.0 


1.283 




—54.40 


15" vac. 


34 


32.062 


42.5 


1.306 




—39.20 


4" vac. 



* Kent's M. E. Pocket-Book. 

t Am. Sch. of Cor. Dickerman-Boyer. 



TABLE 66. 
Table of Salt Brine Solution.* 

(Sodium chloride). 



Degrees 














Salom- 


Percent. 


Pounds 


Specific Si 


)eeific 


Freezing 


Amm. 


eter at 


by wt. 


of salt 


gravity 1 


leat 


point 


gage 


60deg. F. 


of salt 


per eu. ft. 






deg. F. 


pressure 





0.00 


0.000 


l.OOOO 1 


ooo 


32.0 


47.32 


5 


1.25 


0.785 


1.0090 


990 


30.3 


45.10 


10 


2.50 


1.580 


1.0181 


980 


28.6 


43.03 


15 


3.75 


2.401 


1.0271 


970 


26.9 


41.00 


20 


5.00 


8.239 


1.0362 


960 


25.2 


38.96 


25 


6.25 


4.099 


1.0455 


943 


23.6 


37.19 


80 


7.50 


4.967 


1.0547 


926 


22.0 


35.44 


35 


8.75 


5.884 


1.0640 


909 


20.4 


33.69 


40 


10.00 


6.709 


1.0733' 


892 


18.7 


31.93 


45 


11.25 


7.622 


1.0828 


883 


17.1 


30.33 


50 


12.50 


8.542 


1.0923 


874 


15.5 


28.73 


55 


18.75 


9.462 


1.1018 


864 


13.9 


27.24 


60 


15.00 


10.389 


1.1114 


855 


12.2 


25.76 


65 


16.25 


11.384 


1.1213 


848 


10.7 


24.46 


70 


17.50 


12.387 


1.1312 


842 


9.2 


23.16 


75 


18.75 


13.896 


1.1411 


885 


7.7 


21.82 


80 


20.00 


14.421 


1.1511 


829 


6.1 


20.43 


85 


21.25 


15.461 


1.1614 


818 


4.6 


19.16 


90 


22.50 


16.508 


1.1717 


806 


3.1 


18.20 


95 


23.75 


17.555 


1.1820 


795 


1.6 


16.88 


lOO 


25.00 


18.610 


1.1923 


783 


0.0 


15.67 



TABLE 67. 
Horse-Power Required to Produce One Ton of Refrigeration. t 

Condenser pressure and temperature. 





P 


103 


115 


127 


189 


153 


168 


184 


200 


218 


dp 


T 


65 


70 


75 


80 


85 


90 


95 


100 


105 


'2 4 


—20° 


1.0584 


1.1304 


1.2051 


1.2832 


1.3611 


1.4427 


1.5251 


1.60OO 


1.J6910 


■^ 6 


—15 


.9972 


1.0694 


1.1450 


1.2221 


1.30O1 


1.4101 


1.4609 


1.5458 


1.6800 


w & 


—10 


.9026 


.9777 


1.0453 


1.1183 


1.1926 


1.2602 


1.3471 


1.4352 


1.5093 


S 13 


— 5 


.8184 


.8833 


.9537 


1.0280 


1.0935 


1.1679 


1.2437 


1.8209 


1.3961 


?20 





.7352 


.8008 


.8648 


.9328 


1.0019 


1.0718 


1.1467 


1.2194 


1.2547 


5 


.6665' 


.7312 


.7946 


.8593 


.9278 


.9978 


1.0656 


1.1881 


1.2121 


S 24 


10 


.5915 


. .6629 


.7257 


.7894 


.8545 


.9205 


.9911 


1.0595 


1.1294 


U28 


15 


.5410 


.5998 


.6641 


.7276 


.7924 


.8558 


.9224 


.9943 


1.0603 


?.33 


20 


.4745 


.5340 


..5923 


.6716 


.7148 


.7796 


.8420 


.9031 


.9736 


.^39 


25 


.4103 


.4659 


.5227 


.5804 


.5992 


.7022 


.7667 


.8289 


.8922 


*S 45 


30 


.8509 


.4056 


.4612 


.5178 


.5755 


.6358 


.6944 


.7590 


.8172 


(S 51 


85 


.8005 


.3546 


.4101 


.4666 


.5214 


.5804 


.6398 


.7009 


.7629 



Note.— The above flgiires are purely theoretical. 
50 per cent, must be added. 

*Am. Sch. of Cor. Dickerman-Boyer. 
■f De La Vergne Catalog. 



In practice about 



458 



TABLE 68. 

Cubic Feet of Aniinonia Gas per Minute to Produce One Ton 

of Refrigeration per Day.* 

Condenser pressure and temperature. 







Press. 1 


103 


115 


127 


139 


153 


168 


185 


200 


218 


53 


Press. 
4 


Temp. 


65° 


70° 


75° 


80° 


85° 


90° 


95° 


100° 


105° 


S 


—20° 


5.84 


5.90 


5.96 


6.03 


6.06 


6.16 


6.23 


6.30 


6.43 


m "^ 


6 


—15° 


5.35 


5.40 


5.46 


5.. 52 


5.58 


5.64 


5.70 


5.77 


5.83 


g ^ 


9 


—10° 


4.66 


4.73 


4.76 


4.81 


4.86 


4.91 


4.97 


5.05 


5.08 


P,°= 


13 


— 5° 


4.09 


4.12 


4.17 


4.21 


4.25 


4.30 


4.35 


4.40 


4.44 


^ s 


16 


0° 


3.59 


3.63 


3.66 


3.70 


3.74 


3.78 


3.83 


3.87 


3.91 




20 


5° 


3.20 


3.24 


3.27 


3.30 


3.34 


3.38 


3.41 


3.45 


3.49 


24 


10° 


2.87 


2.90 


2.93 


2.96 


2.99 


3.02 


3.06 


3.09 


3.12 


28 


15° 


2.59 


2.61 


2.65 


2.68 


2.71 


2.73 


2.76 


2.80 


2.82 


bo 


S3 


20° 


2.31 


2.34 


2.36 


2.38 


2.41 


2.44 


2.46 


2.49 


2.51 


^ 


39 


25° 


2.06 


2.08 


2.10 


2.12 


2.15 


2.17 


2.20 


2.22 


2.24 


^ 


45 


30° 


1.85 


1.87 


1.89 


1.91 


1.93 


1.95 


1.97 


2.0O 


2.01 




51 


35' 


1.70 


1.72 


1.74 


1.76 


1.77 


1.79 


1.81 


1.83 


1.85 



TABLE 69. 
Table of Refrigerating Capacities.! 











Number o 


E eu. f 


t. per 


ton of refriffera- 


Size oi Duuamg 






tion at temperatures given 






Sur- 


Ratio 






Temperatures 




Dimen- 


Con- 
tents 


face 
in sq. 


eu. ft. 
to sq. 














sions of 














building 


eu. ft. 


ft. 


ft. 


0° 


8° 


16° 


24" 


82° 


40° 


48° 


5x4x5 


ICO 


130 


1.3 


900 


llOO 


1300 


1500 


1700 


1900 


2100 


8x10x10 


80O 


520 


.65 


180O 


2200 


2600 


3000 


340O 


3800 


4200 


25x40x10 


10000 


3300 


.33 


3600 


4400 


5200 


6000 


6700 


7600 


8400 


20x50x20 


20000 


4800 


.24 


4860 


5940 


7020 


8100 


9180 


10260 


11340 


40x50x20 


40000 


7600 


.19 


630O 


7700 


9100 


1050O 


11900 


13300 


14700 


60x50x20 


60000 


10400 


.17 


6840 


8360 


9880' 


11400 


12920 


14440 


15960 


80x50x20 


80000 


1320O 


.165 


7200 


8800 


10700 


120OO 


13600 


15200 


16800 


100x50x20 


100000 


16000 


.16 


720O 


8800 


1O40O 


1200O 


13600 


15200 


16800 


100x100x20 


200000 


28000 


.14 


8100 


9900' 


11700 


1300O 


15300 


17100 


18900 


100x100x40 


400000 


36000 


.09 


13050 


15950 


18850 


21750 


24650 


27550 


30450 


100x100x60 


600000 


44O0O 


.073 


16200 


19800 


23400 


27000 


30600 


34200 


37800 


100x100x80 


800000 


52000 


.065 


180O0 


22000 


26000 


3000O 


340OO 


380OO 


42O0O 


100x100x100 


lOOOOOO 


600OO 


.06 


19350 


23650 


27950 


32250 


36550 


4085O 


45150 



* Featherstone Foundry and Machine Co. Catalog, 
t Tayler. P. B. of R. 



459 



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■* 


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1—1 


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„ 


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^ 


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^ 


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03 


- 


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■* 


" 


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f^fvi 




M 


M 


0:1 


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CO 


CO 


CO 




^ 






























































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03 
























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s 


g 


S 


8 


^ 


8 


10 


8 





s 
















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H 


hft 























460 



TABLE 71. 

Temperatures to Which Ammonia Gas Is Raised by 

Compression.* 



Tempera- 


Absolute 




Absolute suction pressure 




ture of 


condensing 


























suction 


pressure 


20 


25 


30 


35 


40 


45 


deg. F. 


90 


199 


165 


138 


116 


98 


83 




110 


232 


196 


166 


145 


126 


109 




130 


261 


222 


193 


169 


150 


132 




150 


285 


246 


216 


191 


171 


153 




160 


296 


257 


226 


202 


181 


163 


5 deg. F. 


90 


266 


172 


145 


123 


104 


89 




110 


239 


203 


174 


151 


132 


115 




130 


268 


230 


200 


176 


1.56 


139 




150 


293 


254 


223 


198 


178 


160 




160 


305 


265 


234 


209 


188 


170 


10 deg. F. 


90 


213 


178 


151 


129 


110 


96 




110 


247 


210 


181 


158 


139 


122 




130 


275 


237 


207 


183 


163 


145 




150 


301 


262 


231 


205 


185 


167 




160 


313 


273 


241 


216 


195 


176 


15 deg. F. 


90 


221 


185 


1.58 


135 


117 


101 




110 


254 


217 


188 


164 


145 


128 




130 


283 


245 


214 


191 


170 


152 




150 


309 


269 


238 


213 


192 


173 




160 


321 


281 


249 


223 


202 


183 


20 deg. F. 


90 


228 


192 


164 


141 


123 


106 




110 


262 


224 


195 


171 


150 


134 




130 


291 


252 


222 


197 


176 


158 




150 


317 


277 


245 


220 


198 


180 




160 


329 


288 


256 


230 


20O 


190 


25 deg. F. 


90 


235 


199 


171 


148 


129 


111 




110 


269 


230 


200 


178 


155 


140 




130 


299 


259 


229 


204 


183 


165 




150 


325 


284 


253 


227 


205 


187 




160 


338 


296 


264 


237 


216 


197 


30 deg. F. 


90 


242 


206 


177 


154 


134 


118 




110 


277 


239 


208 


184 


164 


147 




1.30 


307 


267 


236 


211 


190 


171 




1.50 


334 


292 


260 


234 


212 


193 




160 


346 


304 


271 


245 


223 


203 


35 deg. F. 


90 


249 


213 


182 


160 


141 


124 




110 


286 


246 


215 


191 


170 


153 




130 


315 


274 


243 


217 


196 


178 




150 


341 


300 


268 


241 


219 


200 




160 


354 


312 


279 


252 


230 


210 



*Tayler. P. B. of R. 



461 



g 




«D 


2 




S3 




00 


1 




0.700 






s 




2 


2 


g 


1 


3 


1 


O 


i 


8 




!N 


1 






^ 


I-H 


i 


o 


in 


s 


(M 




in 




is 


s 




g 


g 


CO 


i 


Ol 


CO 




in 


CD 


d 


i 


^ 


o 
in 


o 


I— 1 


GO 


^ 


o 

CO 


! 


d 


■* 


^ 


§ 


<iO 


O 


CO 




CD 


1 


d 


§g 

CO 

t 


S 


00 

Jo 




g 


o 


1:- 


^ 


CO 


i 

d 


8 


^ 


C-3 


CO 




g 




i 


in 
d 


! 


^ 


00 


5J 


■ ^ 


CO 


in 




00 


d 


in 


o 


C6 


o 


C<1 

■ s 


in 




00 
CO 


1 


d 


i 




lO 




CO 


§ 


O 


CO 


s 
^ 


■= 




o 




00 


in 


i> 


o 

00 


(6 


1 


2 


m 


lO 


■» 

M 




CO 


in 


o 


CO 


1-1 


] 


i 


=> 


o i o 1 o ■ 


o 


o 


o 


^ i i 


rH 


1 


PR 
1 

d 

a 
1 
ft 

1 


7 

8| 
ft 


6 


w 

1 

)J0 


1 


k 
1 

T-l 


1 

Is 

IS 
1 


1 
g I 


b 
8 

iio 


^ .n 
•1 ^ 

3 


I 


a 

C3 

Is" 

■--1 

1 ^ 

3 "^ 


+ 


a 
a 

.S 

.a 

1 


o 


i 

1 


03 CQ 

>> 

O 


Cii o09) -O oS-ST 
•ossy -raoqo 'S 'A 


A 


^lAB 


jS 3gp9 


dS 





462 



TABLE 73. 
Time Required to Freeze Ice in Cells or Cans, (a) (Siebert).* 





Thickness in inches 


Temp. 






deg. P. 


1 


2 


3 


4 


5 


6 


7 
15.6 


8 
20.4 


' 


10 

31.8 


11 


12 


10 


0..'?2 


1.28 


2.86 


5.10 


8.00 


11.5 


25.8 


38.5 


45.8 


12 


O.B.'S 


1.40 


3.15 


5.60 


8.75 


12.6 


17.3 


22.4 


28.4 


35.0 


42.3 


50.4 


14: 


0.39 


1.56 


3.50 


6.22 


9.70 


14.0 


19.0 


25.0 


31.5 


39.0 


47.0 


56.0 


16 


0.44 


1.7.5 


3.94 


7.0O 


11. OO 


15.8 


21.5 


28.0 


35.5 


43.7 


53.0 


6S.0 


18 


0..W 


2.00 


4.. 50 


8.00 


12.. 50 


18.0 


24.5 


32.0 


40.5 


50.0 


60.5 


72.0 


20 


0..5S 


2.32 


5.25 


0..30 


14.60 


21.0 


28.5 


37.3 


47.2 


58.3 


70.5 


84.0 


22 


0.70 


2.80 


6.30 


11.20 


17.. 50 


25.2 


34.3 


44.8 


56.7 


70.0 


84.7 


100.0 


24 


0.88 


3.50 


7.86 


14.00 


21.00 


31.5 


42.8 


56.0 


71.0 


87.5 


106.O 


126.0 



(a) Time required from one wall, for plate ice, two times the above values. 

TABLE 74. 
Standard Sizes of Ice Cans.f 



Size of 


Size of 


Size of 


Inside 


Outside 


Size of 


cake, in 


top, 


bottom, 


depth. 


depth. 


band. 


pounds 


inches 


inches 


inches 


inches 


inches 


50 


8x8 


71/2x71/2 


31 


32 


1/4x11/2 


100 


8x16 


71/4x1.514 


31 


32 


¥4x11/2 


200 


111/2x221/2 


101/2x211/2 


31 


32 


1/4x2 


300 


111/2x221/2 


101/2x211/2 


44 


45 


ViX2 


400 


111/2x221/2 


101/2x211/2 


57 


58 


¥4x2 



TABLE 75. 
Cold Storage Temperatures for Various Articles.* 



Article 



Apples 

Asparagns 

Bananas 

Beans (dried) __ 
Berries (fresh) _ 
Buckwheat 

flour 

Butter 

Cabbage 

Cantaloupes _— 

Celery 

Cheese 

Chocolate 

Cider 

Claret 

Corn (dried) __ 

Cranberries 

Cream 

Cucumbers 

Dates 

Eggs 

Figs 

Fish (fresh) 

Fish (dried) — _ 



Temp. 

deg. 

F. 



32-36 
34 
40-45 
32-40 
36-40 

40 
32-38 

34 

40 
32^34 
32-33 

40 
30-40 
45-50 

35 
34-36 

35 

39 

55 
33-35 

55 
25-30 

35 



Article 



Fruits 

Fruits (dried) _. 
Fruits (canned) 
Furs (un- 
dressed) 

Furs (dressed). 
Game (frozen). 
Game (to 

freeze) 

Grapes 

Hams 

Hopsi 

Honey 

Lard 

Lemons 

Meat (canned). 
Meat (fresh) ._ 
Meat (frozen) _ 

Milk 

Nuts 

Oat meal 

Oil 

Oleomargarine 
Onions 



Temp. 

deg. 

F. 



26-55 

35-40 

35 

35 
25-.32 
25-28 

15-28 



30-35 

33-40 

45 

34-45 

36-40 

35 

34 

2.5-28 

32 

35 

40 

35 

35 

34-40 



Article 



Oranges 


4.5-50 


Oysters 


33-35 


Oysters (in 




tubs) 


25 


Oysters (in 




sheUs) 


33 


Peaches 


45-55 


Pears 


34-36 


Peas (dried) __. 


40 


Pork 


34 


Potatoes 


36-40 


Poultry 




(frozen) 


28-30 


Poultry (to 




freeze) 


18-22 


Sugar, etc. 


40-45 


Syrup 


35 


Tobacco 


35 


Tomatoes 


36 


Vegetables 


34-40 


Watermelons _. 


34 


Wheat flour _._ 


40 


Wines 


40-45 



Temp, 

deg. 

F. 



25-32 



* Tayler. P. B. of R. 

+ As adopted by the Ice Machine Builders' Association of the U. S. 
463 



APPENDIX III. 



Tests of House Heating: Boilers. 

The following- extract from a series of tests on a Num- 
ber S-48-7 Ideal Sectional Boiler from the reports of the 
American Radiator Company's Institute of Thermal Re- 
search, Buffalo, New York, will be of interest. 



Coal 


Coal 


S-48-7 


S-48-7 


7:00 


8:09 


1344.00 


1434.00 


192.00 


178.20 


8.95 


8.35 


72.5. OO 


600.00 


5.60 


5.24 


8.75 


8.77 



Size of Grate 48x64V^ in. Grate area 21.6 sq. ft. 

Heating surface— total 300. Osq. ft. 

Hard Hard Hard 

0— Fuel used in tests Coal 

1— No. of boiler S-48-7 

2— Duration of test hours 8:00 

4— Fuel burned during- test, lbs 1360.00 

5 — Fuel per hour, lbs. 170.00 

6 — Fuel per sq. ft. grate per hour, lbs 7.90 

7 — Stack temperature, degrees Fahrenheit 750.00 

8 — Evaporation per sq. ft. of heating surface 

per hour, lbs. 4.97 

9— Evaporative power available— lbs. of -water 

per lb. of coal 8.80 

10 — Boiler-po-o'er (evaporation per hour) — lbs. 

(item 5 x item 9) 1496.00 1680.00 1562.00 

11— Capacity— sq. ft. (item 10 -4- 0.2-2) 6800.00 7640.00 7100.00 

12— Capacity— sq. ft. (item 10 4- 0.25) 5980.00 6720.00 6250.00 

Catalog rating 5700 sq. ft. 

The accompanying- figure shows the combustion chart 
as developed for this same boiler. The tests were run to 
find the evaporative power and ca- 
pacitij with varying amounts of 
coal burned per hour. Coal was 
fired at regular intervals and the 
steam pressure was maintained at 
two pounds gage on the radiation. 
Line 11 gives the capacity in 
square feet of radiation including 
mains and risers, at the rate of 
.22 pound of steam per square 
foot per hour. Line 12 g-ives the 
capacity at .25 pound of steam per 
square foot per hour. In average 
service about one-third of these 
quantities of coal would be burned. The catalog rating is 
based upon burning 167.5 pounds of coal per hour and an 
evaporation of 8.5 pounds of water per pound of coal (rates 
of combustion and evaporation that seem justifiable). As 
■will be seen from lines 5 and 9 the actual amount of coal 

465 







/ 


1600 
.,500 
3 1400 

i '300 
-«200 

5 noo 
"> aooo 

900 

1 BOO 


















*/ 



DS 
















•/ 
















^ 


atalogu 
Rating 












t 










/ 
















> 
















.A 








S-48 


7 




/ 
















/ 


















/ 


















eoc 








































MARO 


100 125 150 175 2 
COAL BURNED PER HOUR (POUr 



burned and the actual evaporation in each test exceed this 
figure. Multiplying 167.5 by the assumed evaporative rate 
of 8.5 and dividing by .25 = 5700 square feet. Comparing 
with column 2, line 5 times line 9 divided by .25 gives 6720 
square feet, which is above the catalog rating. Test number 
two compared with test number one shows that by increas- 
ing the amount of coal from 170 pounds to 192 pounds per 
hour increases the boiler capacity 740 square feet. 

Data Required for E^stimatin^ Plain Hot Water or 
Steam Plants. 



Name 

of 
room 



o o 



Size of 
room 



Radiators 
Steam or water 



2-1 
5.S 



Remarks: 
Cold floor, 
ceiling, etc. 



Date .__._192___ 

Owner of building- Address 

Architect Address . 

Kind of building Location 

Nearest freight station : 

Temperature in living rooms Kind of fuel used. 

Height of cellar Size of smoke flue 

Items to Estimate on. 

Boiler and foundation 

Smoke pipe and damper 

Thermometers and pressure and safety gages 1— . 

Draft regulation 

Firing tools 

Filling and blow-off connection 

Pipe and fittings 



466 



Sq. ft. of radiation 

Cut-off valves and radiator valves 

Air valves 

Radiator wall shields 

Temperature control 

Humidifying- apparatus 

rioor and ceiling- plates 

Hangers 

Expansion tank 

Cold air ducts, stack boxes and registers. 

Pipe covering 

Bronzing' 

Labor of installation 

Preight and cartage 

Per cent, of profit 

Total bid 

Submitted by 



467 



SKETCHES SHOWING VACUUM SERVICE DETAILS.* 

REDUCING ELL 
NIPPLE MAHMUM JIJLE 



[ ©©©©©©] 



CATf VALVE 
E^LCV A TION- END OUTLET MANIFOLD 




NIPPLE MAxinunazE 




ELEVATION-END OUTLET MANIFOLD 

A B 

Method of installing- return connections from overhead 
manifold coils, using drop legs, traps and dirt strainers. 
A for 6 coils or less, B for more than 6 coils. 



TO HEATINIJ SUPPLY MAIN 




C. Method of installing drip connections from horizontal 
oil separator through grease and oil trap to drain. 

D. Method of dripping steam supply main through drip 
trap into vacuum return, using vertical loop as cooling sur- 
face and dirt pocket. 



=Warren Webster Co. 



468 



CONNECT TO LOW PPE55U0E HCATINS MAIN NOT LC55 
THAN I5'DI5TANT FROM PPE5:iUI?E PEGUlATINIj VALVC 



iUPPLYPlMOPlPi 




NOTE UiTtHU 6CTVCCN PUMP BtJTLCf AWO-SUCTlOW VALVtJ 
ff BOigg rtCD PUMP TO BE^QT Ltia THAN J -Q" 



E. Method of draining- down feed supply risers through 
wet return into a feed water heater. 

F. Method of making connections to gages. 





1^ IL LINE 10 WtUUM GAQt 










fc 


p HOT WATER OUTLET 






2^ r rOiULnONOfMCUUMPUMP 


HOT WATER GENERATOR 




^ 


MfHfe 


"] 


U^ ^ITEAM INLET. 

DRIP 




ENOOFPIPETOBt f=^ 
ON LEVEL --irH 1 


|^^J\3UGTW..PA.NEP 




BOnOMOFRETUlfNL/ 


I ^OJEWiS 


ji 


/ REDUCING ELI, 


UNION 


LfiPOEP THAN PETURN MAIN 


=1 UJ—i 

ECCENTRIG BU3HIN6, 


DIPT JTPAINEP ; /f f ^-^ 
■HtAVr OUTt IRAP/ COWEtT INTO TOP OF VACUUM RETURn\ 






G 




H 





G. Method of installing a suction strainer where return 
main rises to vacuum pump, using fittings for lift pocket. 

H. Method of draining a hot water generator through a 
gate valve, dirt strainer and heavy duty trap. 



469 




^^fflia^=3 FLOOBI 



HI&HEM POINT OF Dm R ETUIJN 



'It AIR UNt 
CONNtGI INTO TOP RETUgN 




CONNailOU TO 6C ON 



RUUW FPOM RA DIATOR 
ICONNCCT TO MET RETURN 



3PE0IAL5WINO GHK.VALVE 



I. Method of installing connections where dry return 
rises and drips into wet returns. 

J. Detail showing return connection from radiators on 
brackets to wet return near floor with air line connections 
through air line trap into dry return near ceiling. 



INEOnOM'liLWHEM SUPPLY M AIN 

M11/EI3IO-0OR "7 

!M OP* RETURN <?=fl/ / 

OR MAIN, OVER lO-OJM C^^iQT^^i 



THIiCONNEOnOM'ltWHEM 
AIR LINE 
LE55 FROM 
BRANCH 



^PLCI AL CHLCH VALVL 
VLNT TRAP 




X>^ CHECK VALVE ^^QJ WAT ER WETEB 

'r^ / I ^K^™^ 

M_M, rtCtCi COOUN&COIl W 



K L 

K. Method of installing drip connection at end of sup- 
ply main, or end of a long supply main branch. 

L. Arrangement of return for modulation system where 
steam is taken from outside source. 



470 



INDEX 



Absolute pressure 15 

temperature 14 
Absorption system of refrig. 364 

absorbers 370 

compared with compression sys. 372 

coolers for 371 

condensers for 369 

elevation of 366 

exchangers for 371 

pumps for 371 
Accelerated systems, hot water 187 
Adaptation of district steam to pri- 
vate plants 338 
Air, amount to burn fuels 26 

circulation, furnace system 78, 112 

composition 35 

duct, fresh 83 

effect upon persons 44 

exhausted, from nozzle, actual 254 

exhausted per hour, plenum sys. 235 

hot, radiator) systems 115 

h. p. in moving 253, 257 

humidity of 46 

leakage, heat loss by 67 

moistiu-e required by 51 

needed, plenum system 235 

purification 43 

required as heat carrier 78 

required per person 40, 42 

temperature at register 85 

valves 161 

velocities, measurement of 54, 249 

velocities of, in convection 52 

velocities, plenum system 249, 237 

washing and humidifying 46, 95, 230 
Ammonia, for one-ton refrig. 459 

solubility in water 455 

strength of liquor 455 
Anchors, types of 288 
Anemometer 54 
Appendix I, tables 1 to 57 

for heating and ventilation 399 
Appendix II, tables .58 to 75 

for refrigeration 453 
Appendix III, Boiler tests, data for 
estimating heating plants, vac- 
uum piping details 464 
Application of heat to solids and 
liquids 20 

of heat to gases 24 
Area of chimney, determination of 57 

of ducts, furnace system 82 

of ducts, indirect system 171, 173 

of ducts, plenum system 237 

of furnace and boiler grates 84, 148, 
166 



Aspirating coils 176 
Atmospheric and vapor systems 130 
Automatic vacuum sys. 203 
valves 209 

Bishop and Babcock sys. 203 
Blast coils, see Coils, 
Blowers, see Fans. 
Boiler, feeding 193, 317 

efficiencies 31 

feed pumps 317 

fittings 149 

types 144, 319 
Boilers, h. w. and st. 144, 319 

capacity and number of 323 

care and use of 199 

radiation supplied by 166, 320 

rating of 166, 320 

tests of 465 
Boiling point of water 21, 412, 415 

of liquids 4.57 
Boyle's law 25 

Brine cooling system, cap. of 385 
British thermal unit 11, 16 
Broomell sys. 133 
Bruckner system 138 
B. t. u. defined 10 

equivalents 11 

lost from buildings 73 
Build, materials, conductivities of 63 

Calcium brine solution 457 
Calorie, defined 10 

compared with B. t. u. 11 
Carbon, amount of air to burn 26 

dioxide defined 36 

dioxide exhaled 42 

dioxide in air 36 

dioxide, tests for 33, 38 
Carpenter, Prof. R. C. 71, 259 
Central Station heating. See district 

heating 275 
Centrifugal pumps 207, 315 
Charles' law 25 
Chimney applications 58 

area, determination of 57 
Chimneys 59 

capacity of 422 
Coal, fuel values of 421 
Coils, arrangement of in pipe heater 
1.53, 179, 221, 245 

aspirating 176 

blower system 240 

direct radiation 153 

heat transmission through 167, 240 

sq. ft. for cooling 381 



471 



472 



INDEX 



surface, plenum system 240 

temp, leaving' Vento 239 
Cold air system of refrig. 355 
Combination systems 103, 149, 224 
Combustion of fuels 26 
Comparison of furnace and other 

systems 76 
Compression system of refrig. 356 
Condensation, dripping from mains 
143, 338 

return to boilers 193 
Condenser, concentric tube 359 

enclosed 360 

exhaust steam 300 

for compression systems 359 

heating surface in 307 

submerged 360 
Conduction 18, 62 
Conductivities of building material 
63, 65 

of radiating surfaces 154, 167 
Conduits, district heating 279 
Convection 18, 62 

heat loss due to 62, 67, 72 
Conversion factors for water 411 
Coolers for weak liquor 371 
Cost of, heating from central sta- 
tion 326 

ice making 385, 461) 
Cowls and vent, heads 60 
Cripps system 137 

Designs, typical — 

central station 289, 327 

furnace 86 

hot water 185 

plenum 267 
Dew point, influence of on refrig. 375 

temperature of air 48 
Dew points of air 418 
Direct-indirect radiation 170 
Direct radiation, tapping list 431 
Dirt strainer, Webster 207 
District heating 275 

adaptation to private plants 338 

amount of radiation supplied by 
one horse-power exhaust steam 
306, 339 

amount of radiation supplied 298 

amount of radiation supplied by 
reheater 310 

application to typical design 289 

boiler feed pumps 317 

boilers 319 

capacity of boiler plant 323 

centrifugal pumps 315 

circulating pumps 313 , 

city water supply 317 

classification 295 

conduits 279 

cost of heating 328 

cost, summary of tests 328 

diameter of mains 302, 334 

dripping condensation from mains 



economizer 321 i 

exhaust steam available 304 1 

future increase 298 
heat available in exhaust steam 292 
heating surface in reheater 307 
high pressure steam heater 312 
hot water systems 295 
layout for conduit mains 285 
power plant layout 327, 333 
pressure drop in mains 334 
radiation in district 298 
radiation supplied by 1 h. p. of ex. 

St. 306,^39 
radiat'n supplied by economizer 321 
radiat'n supplied, per boiler h. p. 320 
regrilation 331 
reheater details 310 
reheater for circulating water 307 
reheater tube surface 308 
service connections 303 
steam available for heating 290 
systems classified 295 
typical design for consideration 289 
velocity of water in mains 312 
water per hr., as heat medium 297 
water to condense one pound of 
steam 305 

Double duct, plenum system 229 

Ducts, furnace system 106 
plenum system 237, 268, 272 

Dunham system 135, 203 

Economizers 321 
Efficiencies of boilers 31, 320 

of furnaces 31, 84 

radiation supplied by 321 

surface 323 
Electric pumps 197 
Electrical heating 350 

future of 352 
Engine, size of for plenum system 264 

water rate 306, 310 
Estimating-, data for 466 
Evaporators for refrig. 361 
Exchangers 371 

Exhaust steam heating 201, 248, 266, 
277, 292, 339 

condensers 306 

radiation supplied 306 

steam available 304 
Expansion joints 287 

tanks 163, 439 
Exposure heat 



Factors of evaporation 447 
Fan-coil system, See plenum system. 

furnace system 113 
Fans and blowers 214 

capacity 450, 451, 452 

drives 262 ■ 

housings 217 

power of engine for 264 

selection of fan for cap. 261 

sizes, approx. 260 

speed of 263 



INDEX 



473 



Piltering, -washing and humidifying 

air 46, 95. 230 
Sittings, steam and hot Avater 157 

table of sizes 440 
Flue gas analysis 17 
Freezing mixtures 454 
Fresh air duct 83, 106, 218 
Fresh air inlet to bldgs. 218 
Friction diagrams, water 442, 443 

in water pipes 438 

of air in pipes 441 

of steam in pipes 334 
Fuel values of Am. coals 421 
Fuels, combustion of 26 
Furnace heating 76 

air circulation within room 78, 113 

foundations 105 

location and setting 105 

pipeless 104 

selection lOO 

sizes 424, 425 
Furnace system, fan 113 
Furnace system, gravity 76 

accelerating circulation 117 

air required as heat can-ier 79 

design of 86 

efficiencies 31, 81 

essentials of 77 

fresh air duct in 83 

grate area in 84 

gross register area in 81 

heat stacks, sizes of 82 

heating surface in 85 

leader pipes in 83 

net vent register in 81 

plans for 89 

points to be calculated in 77 

register temperature 80 

registers 80, 109 

stacks or risers in 82, 110 

suggestions for operating 118 

vent stacks 83 

Gage pressure 15 
Gallon degree calculation 385 
Gas analysis 32 
Gas-steam systems 140 
Generators 368 

Honeywell heat 137 
Grate area, boilers and heaters 144, 
166 

furnaces 84 
Greenhouse heating 177 

Hammer, water 192 

Hawkes system 116 

Heat 10 
application to solids and liquids 20 
application to gases 24 
given off by combustion 26 
given off by persons, lights, etc. 74 
given off by radiators 1.54 
latent 15 

mech. equivalent of 15 
specific 16 



Heat loss, chart 65 

combined with vent, losses 73 

for a 10 room house 88 

for average year 94 

method of estimating 69-73 
Heat losses from bldg. materials 63 

due to conduction 61 

due to convection 67 

due to radiation 63 

due to exposure 69 
Heaters, combination 103, 149 

hot water 144 
Heating, boilers 319 

capacity, performance to guaran- 
tee 74 

district 275 

electric 350 

furnace 76 

hot water and steam 120 

mech. vacuum 200 

plenum 213 

surface in boilers 148, 320 

surface in coils 240 

surface in economizer 323 

surface in reheater 307, 309 

systems, comparison of 76, 120, 200, 
213 
High pressure heater 312 

velocity h. w. systems 137 
Honeywell sys. 137 
Horse-power, in moving air 257 

of boilers 320 

of engine 264 

of fan 259 
Hot-air pipes, cap. of 424 

air radiator systems 115 

ducts 83 

stacks 82 
Hot water and steam heating 120 

accelerated or high press, h. w. sys- 
tems 136 

calculation of rad. sur. 167 

classifications 121-124 

connection to radiators 128, 1.53, 
173, 185, 431 

design, h. w. 185 

determination of pipe sizes 180, a34 

diagrams for 125 

empirical equations 170 

expansion tanks 163 

fittings 1.57 

for district service 275 

for tanks and pools 198 

grate area 148, 166 

greenhouse radiation 178 

location of radiators for 185 

main and riser layouts 126, 182, 188, 
191 

pipes, tables of sizes 430 

pitch of mains for 184 

principles of design of 166 

radiators! 1.50 

risers, capacity table 433, 434, 4.35 

proportioning pipe sizes 182 

suggestions for operating 199 



474 



INDEX 



sys., accelerated or high vel. 136 

systems, h. w. and st. 125 

systems, vapor 130 

temperature 331 

water used in indirect coils 247 
Housing-, effect on radiators 155 
Humidity, abs. rel. 46 

effect upon persons 44 

tables of 416, 417 
Hydrometric scales compared 462 
Hygrodeik 47 
Hygrometer 46, 48 
Hygrometric chart 49 

Ice making and refrig, 356, 3S4 

capacity, calculation 384 

cost of 385 
Illinois sys. 135 
Indirect radiators 122, 173 
Insulation of st. and h. w. pipes 191, 
279 

(K) values for coils, radiators 154, 241 
Koerting system 138 

Latent heat 15 
Leader pipes 83 
Location of furnaces 105 

of radiators 185 

of registers 103, 109, 112, 117 

of stacks 82, 90, 110 

Main and riser layout 126, 182, 184, 

188, 191 
Mains, cap. of hot water 180, 433, 434 

cap. of steam 180, 334, 435-437 

condensation from 181, 338 

diameter of, calculation 180, 334 

pitch of 184 

pressure drop and diam. of 299, 334 

velocity of water in 302 
Manholes 289 
Measurement of air velocities 54, 249 

of temperatures 10 
Mechanical equivalent of heat 15 
Mechanical vacuum sys. 200 

advantages of 200 

Automatic, Bishop and Babcock, 
Dunham, Illinois, Webster 203 

dirt strainers for 206, 207 

pump capacities for 206, 208 

radiation for 169 

regulation for 206 

return line valves for 209, 210 
Mechanical warm air sys. See Ple- 
num sys. 
Mills system (attic main) 127 
Moisture, addition of, to air 51 

effect upon persons 44 
Moline sys. 134 
Mouat-Squires sys. 133 

Naperian logarithms 411 
Nitrogen 36 
(n) values of 71 



Operation of furnaces 118 
of hot water heaters and steam 
boilers 199 
Outside temp, for design 92 
Oxygen 36 

Paul system 203 

piping connections for 204 
Performance to guarantee heating 

capacity 74 
Pipe, coil radiators 153, 179, 221, 245 

connections 266 

equalization of sizes 432 

fittings 141, 157, 440 

for refrigeration 363 

leader 83 

hne refrigeration 376 

sizes, determination of ISO, 182, 302, 
334 
Pipeless furnace 104 
Pipes, capacities of 433-437 

for refrigeration 363 
Piping connection around heater and 
engine 266 

corrosion of piping 165 

for heating sys, definitions 120-128 

system for automatic control of 
vacuum 206 
Pitot tubes 55, 255 
Plans, and specifications 388 

of typical Cent, station 327 

of typical furnace sys. 89 

of typical hot water sys. 188 

of typical plenum sys. 268 
Plenum system, meeh. warm air sys. 
213 

air needed cu. ft. per hour in 235 

air velocity 237 

air velocity, theoretical 249 

air washing and humidifying 230 

amount of steam condensed 248 

apphcation of to school bldgs. 267 

approximate rules for 244, 254, 259 

approximate sizes of fan wheels 260 

arrangement of coils in pipe heat- 
ers 245 

arrangement of sees, and stacks in 
Vento heaters 246 

blower fans, actual h. p. to move 
air 257 

Carpenter's rules for 259 

cast surface for 223 

coil surface in 240 

cross sectional area duets, regis- 
ters, etc. 237 

data 267 

division of coil surface in 223 

double ducts in 229 

dry steam needed in excess of exh. 
from engine 248 

efficiency and air temp. 236, 239-242 

factors for change of velocity and 
volume 251-2.53 

fan drives for 262 

final air temperature in 236, 238 



INDEX 



475 



floor plans for 268-274 

heating- surface in coils of 240 

heating- surfaces 220 

h. p. of engine for fan for 264 

h. p. to move air 253, 257-260 

(K) values of 154, 241 

piping connections around heater 
and engine 266 

pressure and velocity, results of 
tests of 254 

single duct in 228 

speed of fans for 263 

split system 228, 271 

temp, of air at register 236 

temp, of air leaving coils 238 

total heat loss per hour 235, 267 

use of hot water in indirect coils 247 

vel. of air escaping to atmos. 252 

work done in moving air 257 
Pools, heating water for 198 
Power, definition 19 

plant layout 327, 333 
Pressed steel radiators 150, 158 
Pressure, absolute 15 

and velocity, results of tests 254 

gage 15 

in water mains 298 
Properties of air 417 

of ammonia 454 

of carbon dioxide 456 

of steami 407 

of sulphur dioxide 456 
Psychrometer, sling- 48 
Psychrometric chart 418 
Pumps, boiler feed 197, 317 

centrifugal 207, 315 

circulating- 313 

city water supply 317 

electric 197 

for absorption system 371 

power required for 314-319 

steam needed for 294 
Purification of air 43 

Radiation 17 

amount of, one sq. ft. reheater 
tube surface will supply .310 

amt. supplied by one h. p. 306 

amt. supplied by economizer 321 

direct-indirect 170 

indirect 122, 173 

hot water and steam 167 

one lb. exh. steam will supply .305 

sur. to heat circulating water 306 
Radiators, amt. of surface on 158 

cast 150, 1.58, 223 

classification of 150 

direct 121 

direct-indirect 121 

effect of housing 1.55 

hot-air, systems 115 

indirect 122 

location and connection of 185 

pipe coil 150, 221 

pressed steel 150, 158 



sizes 158, 173 

sizes, etc., for ten room house 187 

surface calculation for 167 

surface effect on trans, of heat 154 

tapping list 431, 433 
Reck system 139 
Rectifiers 368 
Rector system 115 
Refrigeration 353 

absorbers 370 

absorption system, elevation of 366 

capacities 459 

capacity of brine cooled system 385 

circulating- system 372 

classification of systems 353 

coils, sq. ft. cooling 381 

cold air system 355 

comparison of systems 372 

compression system 355 

condenser 369 

coolers for weak liquor 371 

costs of ice making 385, 460 

evaporators 361 

exchangers 371 

gallon degree calculation 385 

general application 383 

generators 368 

heat loss 379 

horse-power for 458 

ice making cap. calculation 384 

influence of dew point 375 

methods of maintaining low temp. 
.375 

pipe line 376 

pipes, valves and fittings 363 

pump for absorption system 371 

rectifiers .368 

vacuum system 354 
Register, area of 81, 423, 424 

connections 109 

inlets 219 

temperatures 80, 237 
Regulation, district heating- 331 

damper 219, 225 

large plants 343 

small plants 341 
Room temperatures, standard 73 

Salt brine solution 458 
Service connections 288, 303 
Sheet metal dimensions 426 
Single duct, plenum system 228 
Sizes, of fan wheels, approximate 260 

of ice cans 463 
Smoke flues, equalization of 423 
Specific heat 16 

heats, etc., of substances 428 
Specifications for plans 388 

for boilers 145, 187 
Speeds of blower fans 263 
Split sys. plenum heating- 228, 271 
Splitters 2l9 
Squares, cubes, etc, 400 
Stacks and risers 82, 110 



476 



INDEX 



Steam, and hot water heating- 120 
See also h, w. and st. heat. 

amt. condensed in plenum sys. 248 

available for heating circulating 
water 304 

boilers 319 

calculation of rad. sur. 167 

classifications 121-124 

connection to radiators 128, 153, 173, 
185, 431 

condensed per sq. ft. of heating 
sur. per hour 182, 248 

determination of pipe sizes 180, 334 

diagrams for 125 

dry, needed in excess of engine ex- 
haust 248, 290-295, 339 

empirical equations 170 

fittings 157 

g-as-system 140 

grate area 148, 166 

greenhouse rad. 178 

heater, high pressure 312 

heating-, district 289, 298 

location of radiators for 185 

loop 195 

main and riser layouts 126, 182 

mains, diameter of 334, 435-437 

pipe insulation 191, 279 

pipe sizes, table of 430 

pitch of the mains for 184 

principles of design of 166 

properties of sat. 407 

proportioning- pipe sizes 182 

radiators 150 

risers, capacity tables 433-435 

sealed returns 128 

suggestions for operating 199 

systems, h. w. and st. 125 

systems, vapor 130 

traps, hig-h pressure 195 

used by engines 306, 310 
Street mains and conduits, layout 285 
Suggestions for operating, furnaces 
118 

for school districts 395 

for specifications 388 

hot water heaters and boilers 199 
Sylphon damper regulator 136, 149 
Systems, comparison of heating 76, 
120, 200, 213 

Table I radiation constants 17 
Table II determination of CO2 40 
Tables III, IV volume of air per per- 
son 42 
Table V ave. temp, chimney gases 54 
Table VI values of (K) 63 
Table VII exposure losses 69 
Table VIII values of (n) 71 
Table IX standard room temps. 73 
Table X temps, unheated rooms 73 
Table XI heat g^iven off by persons, 

hg-hts, etc. 74 
Table XII calculations for 10 room 
house 88 



Table XIII radiator surfaces 158 
Table XIV indirect rad, sur. 173 
Table XV cap. of indirect rads. 174 
Table XVI cap. greenhouse rad'n 178 
Tables XVII, XVIII, XIX proportion- 
ing- pipe sizes 183 
Table XX cal. data for 10 room 

house 187 
Table XXI cap. Marsh vac. pumps 206 
Table XXII cap. Nash vac. pumps 

208 
Table XXIII sur. Vento heaters 224 
Table XXIV plenum air vel. 2.37 
Table XXV temps, leaving- steam 

coils 239 
Table XXVI temps, leaving^ Vento 

coils 2.39 
Table XXVII values of (c) 241 
Table XXVIII efficiencies of coil 

heaters 241 
Table XXIX efficiencies of coil heat- 
ers 242 
Table XXX air pressure vel. 251 
Table XXXI air pressure, vel. 252 
Table XXXII air pressure, vel. 253 
Table XXXIII approx. fan sizes 260 
Table XXXIV fans speed 263 
Table XXXV cal. data for school 

building-s 267 
Table XXXVI heat loss from conduit 

mains 2'84 
Tables XXXVII, XXXVIII friction 

loss in conduit mains 301, 302 
Table XXXIX diameeters of conduit 

mains 340 
Table XL heat loss through insula- 
tion 379 
Table 1 squares, cubes, etc. 400 
Table 2 trigonometric functions 406 
Table 3 equivalents of units 406 
Table 4 properties of steam 407 
Table 5 Naperian logarithms 411 
Table water conversion factors 411 
Table 7 vol. and wt. of dry air 412 
Table 8 Boiling- temp, at- different 

elevation 412 
Table 9 weig-ht of pure water 413 
Table 10 boiling- points of water in 

vacuum 415 
Table 11 wt. of water and air 415 
Table 12 relative humidities 416 
Table 13 properties; of air 417 
Table 14 dew points of air 418 
Table 15 fuel value of Am. coals 421 
Table 16 capacities of chimneys 422 
Table 17 Excelsior wall stacks 422 
Table 18 equalization of smoke flues 

423 
Table 19 dimensions of reg-isters 423 
Table 20 cap. of furnaces 424 
Table 21 cap. hot air pipes and regs. 

424 
Table 22 cap. of furnaces 425 
Table 23 area of vertical hot air 
flues 425 



INDEX 



477 



Table 24 sheet metal sizes 426 
Table 25 weight of G. I. pipe and el- 
bows 427 
Table 26 sp. ht., etc., of substances 

428 
Tables 27, 28 water pressures at vari- 
ous heads 420 
Table 29 wrought iron pipe sizes 430 
Table 30 expansion of pipes 431 
Table 31 tapping list of direct rads. 

431 
Table 32 pipe equalization 432 
Table 33 sizes of h. w. mains 433 
Table 34 Sizes of h. w. branches and 

risers 433 
Table 35 sizes of h. w. rad. tappings 

433 
Table 36 Honeywell pipe sizes 434 
Table 37 cap. of h. w. mains and 

risers 434 
Table 38 cap. of st. and ret. pipes 435 
Table 39 sizes of st. mains 436 
Table 40 sizes of st. and ret. lines 437 
Table 41 sizes of rad. connections 437 
Table 42 friction in water pipes 438 
Table 43 grav. and vac. returns 439 
Table 44 expansion tanks 439 
Table 45 sizes of flanged fitgs. 440 
Table 46 sizes of pipe fittings 440 
Table 47 friction in air pipes 441 
Table 48 temp, for testing steam 

plants 444 
Table 49 Kewanee boilers 445 
Table 50 heat trans, through pipe 

covering 446 
Table 51 factors of evap. 447 
Table 52 heat in feed water 447 
Table 53 sizes of Vento heaters 448 
Table 54 steam used by engines 449 
Tables 55, 56, .57 speeds, cap., h. p. 

of various fans 450, 451, 

452 
Table 58 freezing mixtures 454 
Table 59 properties of ammonia 4.54 
Table 60 sol. of ammonia in water 

4.55 
Table 61 strength of ammonia liquor 

4.55 
Table 62 prop, of sulphur dioxide 456 
Table 63 prop, of carbon dioxide 456 
Table 64 boiling points of liquids 4.57 
Table 65 calcium brine sol. 457 
Table 66 salt brine sol. 4.58 
Table 67 horse-power for refrig. 458 
Table 68 ammonia for one-ton refrig. 

459 
Table 69 refrigeration caps. 4.59 
Table 70 cost of ice making 460 
Table 71 temp, of ammonia under 

comp. 461 
Table 72 comparison of hydrometer 

scales 462 
Table 73 time req'd to freeze ice 463 
Table 74 sizes of ice cans 463 



Table 75 req'd temp, for cold storage 

463 
Tanks, expansion 163 
Temperature absolute 14 

best outside for design 92 

chart 93 
Tapping list for direct rad. 431, 433 
Temp, control, in heating sys. 341 

important points in 344 

in large plants 343 

in small plants 342' 

Johnson, National Powers sys. 
345-349 
Temperatures, absolute 14 

best to use in heat calculation 73 

for cold storage 463 

for testing plants 444 

of air and rad. in greenhouses 178 

of air entering rooms 80, 236 

of air leaving coils in plenum sys- 
tem 239, 242 

of ammonia under comp. 461 

measurement of high 11 

methods of maintaining low 373 

standard room 73 
Tests to guarantee heat capacity 74 
Thermometers 11 

wet and dry bulb for hygrometer 48 
Thermostat 342, 346 
Thermostatic valves 209, 228 
Time reg. to freeze ice 463 
Traps, steam 194, 195 
Trigonometric functions 406 

Under-feed furnaces 102' 

Use of hot water in indirect coils 247 

Vacuum and gravity returns com- 
pared 439 
Vacuum sys. steam 130, 200 

of refrigeration 354 
Values of (K) 63, 154, 167, 241 

of (n) 71 
Valves, air 161 

check 161 

main supply 159 

radiator supply 160 

return line automatic 209, 210 

thermostatic 209, 228 
Vapor, atmospheric and, sys. 130 
Velocity of air by appl. of heat 52 

of air escaping to atmosphere 252 
Vent., heads and cowls 60 

registers (net) 81 

stacks 83' 
Ventilation, defined 43 

air required per person 40 

heat loss 72 
Vento heaters 223, 224, 239 

sizes 448 ' 
Vertical hot air flues 42.5 
Volume and wt. of air 412, 415 



478 



INDEX 



Warm air fur., cap. of 424, 425 
Washing' and humidifying- air 46, 95, 

230 
Water, conversion factors 411 

hammer 192 

height of cokimn corresponding to 
pressures in ounces 429 

needed per hour in dist. heatg. 297 

pressure in mains 298 

sealed returns 128 

weight of pure 413, 414 



weight of, and air 415 
Webster sys. 135, 203 
Weight, and sizes of sheet metal 426 

of G. I. pipe 427 

of pure water 413, 414 

of water and air 415 
Work, definition 19 

done in moving air 253, 257 
Wrought iron and steel pipe sizes 430 

Zellweger fan 232 



OCT ^ 



mi 



«l 



